## Chapter 8 - Simultaneous Linear Equations Exercise Ex. 8.1

Question 1
Solve the following simultaneous equations by the substitution method:
2x + y = 8
3y = 3 + 4x
Solution 1
Question 2
Solve the following simultaneous equations by the substitution method:
x + 3y= 5
7x - 8y = 6
Solution 2
Question 3
Solve the following simultaneous equations by the substitution method: 5x + 4y - 23 = 0
x + 9 = 6y
Solution 3
Question 4
Solve the following simultaneous equations by the substitution method:
2x + 3y = 31
5x - 4 = 3y
Solution 4
Question 5
Solve the following simultaneous equations by the substitution method:
7x - 3y = 31
9x - 5y = 41
Solution 5
Question 6
Solve the following simultaneous equations by the substitution method:
13 + 2y = 9x
3y = 7x
Solution 6
Question 7
Solve the following simultaneous equations by the substitution method:
0.5x + 0.7y = 0.74
0.3x + 0.5y = 0.5
Solution 7
Question 8
Solve the following simultaneous equations by the substitution method:
0.4x + 0.3y = 1.7
0.7x - 0.2y = 0.8
Solution 8

Question 9
Solve the following simultaneous equations by the substitution method:
3 - (x + 5) = y + 2
2(x + y) = 10 + 2y
Solution 9
Question 10
Solve the following simultaneous equations by the substitution method:
7(y + 3) - 2(x + 2) = 14
4(y - 2) + 3(x - 3) = 2
Solution 10
Question 11
Solve the following simultaneous equations:
13a - 11b = 70
11a - 13b = 74
Solution 11
Question 12
Solve the following simultaneous equations:
41x + 53y = 135
53x + 41y = 147
Solution 12
Question 13
Solve the following simultaneous equations:
65x - 33y = 97
33x - 65y = 1
Solution 13
Question 14
Solve the following simultaneous equations:
103a + 51b = 617
97a + 49b = 583
Solution 14
Question 15
Solve the following pairs of equations:

Solution 15
Question 16
Solve the following pairs of equations:

Solution 16
Question 17
Solve the following pairs of equations:

Solution 17
Question 18
Solve the following pairs of equations:

Solution 18
Question 19
Solve the following pairs of equations:

Solution 19
Question 20
Solve the following pairs of equations:

Where x ≠ 0, y ≠ 0
Solution 20
Question 21
Solve the following pairs of equations:

Solution 21
Question 22
Solve the following pairs of equations:

Solution 22
Question 23
Solve the following pairs of equations:

Where x + y ≠ 0 and x - y ≠ 0
Solution 23
Question 24
Solve the following pairs of equations:

Solution 24

Question 25
Solve the following pairs of equations:

Solution 25
Question 26
Solve the following pairs of equations:

Solution 26
Question 27
Can the following equations hold simultaneously?
7y - 3x = 7
5y - 11x = 87
5x + 4y = 43
If yes, find the value of x and y.
Solution 27
Question 28
If the following three equations hold simultaneously for x and y, find the value of 'm'.
2x + 3y + 6 = 0
4x - 3y - 8 = 0
x + my - 1 = 0
Solution 28
Question 29
Solution 29
Question 30
Solution 30
Question 31
Solution 31
Question 32
Solution 32
Question 33
Solution 33

## Chapter 8 - Simultaneous Linear Equations Exercise Ex. 8.2

Question 1
Draw the graphs of the following linear equations:
x = 3
Solution 1
The graph of x = 3 is as follows:

Question 2
Draw the graphs of the following linear equations:
y + 5 = 0
Solution 2
Given equation, y + 5 = 0
i.e. y = -5

The graph is as follows:

Question 3
Draw the graphs of the following linear equations:
3x + 2y - 6 = 0
Solution 3

Question 4
Draw the graphs of the following linear equations:
5x - 5y = 8
Solution 4

Question 5
Draw the graph for each of the following equation: Also, find the coordinates of the points where the graph of the equation meets the coordinate axes:

Solution 5

Thus, the graph of the equation meets the X-axis at (2, 0) and Y-axis at (0, 3).
Question 6
Draw the graph for each of the following equation: Also, find the coordinates of the points where the graph of the equation meets the coordinate axes:
Solution 6

Thus, the graph of the equation meets the X-axis at (-6, 0) and Y-axis at (0, 45).
Question 7
Draw the graph of the equation 4x - 3y + 12 = 0.
Also, find the area of the triangle formed by the line drawn and the coordinate axes.
Solution 7

Question 8
Draw the graph of the equation
y = 5x - 4 Find graphically
a. the value of x, when y = 1
b. the value of y, when x = -2
Solution 8

From the graph, we find that

a. When y = 1, x = 1.
b. When x = -2, y = -14
Question 9
Use the given table and draw the graph of a straight line.
 x 1 2 3 P y 1 q -5 7

Find graphically the values of 'p' and 'q'.
Solution 9
The graph is as follows:

From the graph, we find that p = -1 and q = -2.

Question 10
A straight line passes through the points (2, 5) and (-4, -7). Plot these points on a graph paper and draw the straight line passes through these points. If points (a, -1) and (-5, b) lie on the line drawn, find the value of a and b.
Solution 10
The graph is as follows:

From the graph, we find that a = -1 and b = -9.
Question 11
Solve the following system of equations graphically:
2x = 23 - 3y
5x = 20 + 8y
Also, find the area of the triangle formed by these lines and x-axis in each graph.
Solution 11

Question 12
Solve the following system of equations graphically:
6x - 3y + 2 = 7x + 1
5x + 1 = 4x - y + 2
Also, find the area of the triangle formed by these lines and x-axis in each graph.
Solution 12

Question 13
Solution 13
Question 14
Solution 14
Question 15
Solution 15
Question 16
Solution 16
Question 17
Solution 17

## Chapter 8 - Simultaneous Linear Equations Exercise Ex. 8.3

Question 1
The length of a rectangle is twice its width. If its perimeter is 30 units, find its dimensions.
Solution 1
Question 2
The difference of two numbers is 3, and the sum of three times the larger one and twice the smaller one is 19. Find the two numbers.
Solution 2
Question 3
If a number is thrice the other and their sum is 68, find the numbers.
Solution 3
Question 4
The sum of four times the first number and three times the second number is 15. The difference of three times the first number and twice the second number is 7. Find the numbers.
Solution 4
Question 5
In a two-digit number, the sum of the digits is 7. The difference of the number obtained by reversing the digits and the number itself is 9. Find the number.
Solution 5
Question 6
The sum of a two-digit number and the number obtained by reversing the digits is 110 and the difference of two digits is 2. Find the number.
Solution 6
Question 7
Seven more than a 2-digit number is equal to two less than the number obtained by reversing the digits. The sum of the digits is 5. Find the number.
Solution 7
Question 8
If 2 is added to the numerator and denominator it becomes  and if 3 is subtracted from the numerator and denominator it becomes Find the fraction.
Solution 8

Question 9
The ratio of two numbers is . If 4 is added in first and 32 is subtracted from the second, the ratio becomes the reciprocal of the original ratio. Find the numbers.
Solution 9
Question 10
The sum of the numerator and denominator of a fraction is 12. If the denominator is increased by 3, the fraction becomes . Find the fraction.
Solution 10
Question 11
If 1 is added to the denominator of a fraction, the fraction becomes If 1 is added to the numerator of the fraction, the fraction becomes 1. Find the fraction.
Solution 11
Question 12
The age of the father is seven times the age of the son. Ten years later, the age of the father will be thrice the age of the son. Find their present ages.
Solution 12
Question 13
The present ages of Kapil and Karuna are in the ratio 2 : 3. Six years later, the ratio will be 5 : 7. Find their present ages.
Solution 13
Question 14
A father's age is three times the age of his child. After 12 years, twice the age of father will be 36 more than thrice the age of his child. Find his present age.
* Question modified
Solution 14
* Question modified
Question 15
In a triangle, the sum of two angles is equal to the third angle. If the difference between these two angles is 20°, determine all the angles.
Solution 15
Question 16
In a ABC, A = x°, B = (2x - 30)°, C = y° and also, A + B = one right angle. Find the angles. Also, state the type of this triangle.
Solution 16
Question 17
A two-digit number is such that the ten's digit exceeds thrice the unit's digit by 3 and the number obtained by interchanging the digits is 2 more than twice the sum of the digits. Find the number.
Solution 17
Question 18
Anil and Sunita have incomes in the ratio 3 : 5. If they spend in the ratio 1 : 3, each saves T 5000. Find the income of each.
Solution 18
Question 19
The ratio of passed and failed students in an examination was 3 : 1. Had 30 less appeared and 10 less failed, the ratio of passes to failures would have been 13 : 4. Find the number of students who appeared for the examination.
Solution 19
Question 20
An eraser costs Rs. 1.50 less than a sharpener. Also, the cost of 4 erasers and 3 sharpeners is Rs.29. Taking x and y as the costs (in Rs.) of an eraser and a sharpener respectively, write two equations for the above statements and find the value of x and y.
Solution 20
Question 21
A person goes 8 km downstream in 40 minutes and returns in 1 hour. Determine the speed of the person in still water and the speed of the stream.
Solution 21
Question 22
A boat goes 18 km upstream in 3 hours and 24 km downstream in 2 hours. Find the speed of the boat in still water and the speed of the stream.
Solution 22
Question 23
Salman and Kirti start at the same time from two places 28 km apart. If they walk in the same direction, Salman overtakes Kirti in 28 hours but if they walk in the opposite directions, they meet in 4 hours. Find their speeds (in km/h).
Solution 23
Question 24
A solution containing 12% alcohol is to be mixed with a solution containing 4% alcohol to make 20 gallons of solution containing 9% alcohol. How much of each solution should be used?
Solution 24
Question 25
9 pens and 5 pencils cost Rs.32, and 7 pens and 8 pencils cost Rs.29. Find the unit price for each pen and pencil.
Solution 25
Question 26
Sunil and Kafeel both have some oranges. If Sunil gives 2 oranges to Kafeel, then Kafeel will have thrice as many as Sunil. And if Kafeel gives 2 oranges to Sunil, then they will have the same numbers of oranges. How many oranges does each have?
Solution 26
Question 27
Samidha and Shreya have pocket money Rs.x and Rs.y respectively at the beginning of a week. They both spend money throughout the week. At the end of the week, Samidha spends Rs.500 and is left with as much money as Shreya had in the beginning of the week. Shreya spends Rs.500 and is left with of what Samidha had in the beginning of the week. Find their pocket money.
Solution 27
Question 28
Two mobiles S1 and S2 are sold for Rs. 10,490 making 4% profit on S1 and 6% on S2. If the two mobiles are sold for Rs.10,510, a profit of 6% is made on S1 and 4% on S2. Find the cost price of both the mobiles.
Solution 28
Question 29
A and B can build a wall in days. If A's one day work is of one day work of B, find in 4 how many days A and B alone can build the wall.
Solution 29