MATH QUESTIONS FOR CLASS 8 WITH ANSWERS

Math Questions for Class 8 with Answers :

In this section, we will see some practice questions for 8th grade students.

Question 1 :

Find the value of x in 12 : 16 :: x : 20

(A) 14               (B) 14               (C) 15

Solution :

Since the given two ratios are in proportion, we have to equate the ratios.

(12 / 16)  =  (x / 20)

x  =  12 (20)/16

x  =  3(5)

  =  15

So, the value of x is 15.

Question 2 :

A fort had enough food for 120 soldiers for 200 days. After 5 days 30 soldiers leave the fort. How long will the remaining food last now?

(A) 260 days         (B) 140 days           (C) 120 days

Solution :

Lets assume required food per person per day=x

Food for 120 people for 1 day  =  120x

Total available food  =  120x (200)

Total food  =  24000x

Food consumed in 5 days  =  120x (5)  =  600x

Food left after 5 days  =  24000x - 600x

  =  23400x

As 30 people died after 5 days, remaining people 90

Food required for 90 people for day  =  90x

No of days food can be consumed for 90 people  =  food left/food consumption per day

  =  23400x/90x

  =  260

So remaining food will be last for another 260 days.

Question 3 :

If a scooter travels 155 km on 5 liters of petrol, how many kilometers will it travel on 9 liters of petrol ? 

(A) 139 km           (B) 279 km         (C) 100 km

Solution :

Distance traveled by the scooter by consuming 5 liters of petrol  =  155 km

Distance traveled by consuming 1 liter of petrol  =  155/5

  =  31 km

Number of km traveled by the scooter by consuming 9 liters of petrol  =  31 ⋅ 9

  =  279 km 

Question 4 :

If 20 men can build a wall 112 meters long in 6 days, what length of a similar wall can be built by 25 men in 3 days?

(A) 80 meters          (B) 70 meters          (C) 20 meters

Solution :

Step 1 :

Consider the number of men and the length of the wall. As the number of men increases from 20 to 25, the length of the wall also increases. So it is in Direct Variation.

So, the proportion is 20 : 25 :: 112 : x ...... (1)

Step 2 :

Consider the number of days and the length of the wall. As the number of days decreases from 6 to 3, the length of the wall also decreases. So, it is in Direct Variation.

So, the proportion is 6 : 3 :: 112 : x ..... (2)

Combining (1) and (2), we can write

20 ⋅ 6 ⋅ x  =  25 ⋅ 3 ⋅ 112

x  =  (25 ⋅ 3 ⋅ 112) / (20 ⋅ 6)

x  =  70 meter

Question 5 :

ABCD is a parallelogram in which angle of DAB and DBC 75°, 60° respectively. Calculate the angles CDB and ADB.

(A)  49°, 51°        (B)  45°, 60°          (C)  21°, 75°

Solution :

<DAB + <ADC  =  180

75 + <ADC  =  180

<ADC  =  180 - 75  =  65°

<ADC  =  <ADB + <BDC  -----(1)

105  =  60 + <BDC

105 - 60  =  <BDC

<BDC  =  45°

<ADB  =  60° (Alternate angles)

Hence the required angles are 45° and 60° 

Question 6 :

If the selling price of 10 articles is equal to the cost price of 11 articles.Find the profit percent.

(A) 15%           (B) 10%          (C) 12%

Solution :

Now we calculate the cost price of 9 articles.

Cost price of 9 articles = 1 x 9 = $ 9

Thus,

Profit made on the selling of 9 articles

  =  Selling price of 9 articles - Cost price of 9 articles

Profit made on the selling of 9 articles = 10 - 9

Profit made on the selling of 9 articles = $ 1

% Profit or % Gain = ( Profit / Cost Price ) x 100 %

% Gain = ( 1 / 9 ) x 100 %

% Gain = 11.11 %

Hence the answer is 12%

Question 7 :

Find AC when AB = 15 cm, AD = 10 cm, AE = 8 cm

(A)  12 cm       (B)  10 cm        (C)   13 cm

Solution :

DE || BC

AD / DB  = AE / EC  ------(1)

AB = 15 cm

AD + DB  =  15

10 + DB  =  15

DB  =  15 - 10  =  5 cm

AD = 10 cm, AE = 8 cm

Applying these values in the first equation, we get

10 / 5  =  8 / EC

EC  =  8 (5) / 10

EC  =  4  cm

AC  =  AE + EC  ==>  8 + 4  =  12 cm

Hence the length of AC is 12 cm.

Question 8 :

Angle ABC measures 250°, find the measure of minor of arc AC.

(A)  150°          (B)  110°         (C)  140°

Solution :

<ACB  =  360 - 250

  =  110°

Hence the required angle is 110°.

Question 9 :

Find the mean of all odd numbers between 80 and 88.

(A) 84            (B) 30             (C) 62

Solution :

To find the mean of odd numbers between 80 and 88.

let us list out the numbers between 80 and 88.

81, 82, 83, 84, 85, 86, 87

Odd numbers are 81, 83, 85 and 87.

Mean  =  (81 + 83 + 85 + 87)/4

  =  336/4

  =  84

Question 10 :

The number of times a particular observation occur in a data is called its __________

(A) Frequency          (B) Mean         (C) Median

Solution :

The number of times a particular observation occur in a data is called its frequency.

After having gone through the stuff given above, we hope that the students would have practiced questions given above.

Apart from the stuff given on, if you need any other stuff in math, please use our google custom search here. 

Kindly mail your feedback to v4formath@gmail.com

We always appreciate your feedback.