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8th Grade > Mathematics

DIRECT AND INVERSE PROPORTIONS MCQs

Total Questions : 58 | Page 2 of 6 pages
Question 11. Rashmi has a road map with a scale of 1 cm representing 18 km. She drives on a road for 72 km. What would be her distance covered in the map?
  1.    4 cm
  2.    6 cm
  3.    9 cm
  4.    8.2 cm
 Discuss Question
Answer: Option A. -> 4 cm
:
A
Let us assume that her distance covered in cm in the map be x.
Rashmi Has A Road Map With A Scale Of 1 Cm Representing 18 K...
The scale and kilometer it representare directly proportional
AB= Constant
A1B1 =A2B2
18 x = 72
x = 7218=4cm
Question 12. The Claude crayon company can make 2400 crayons in 4 minutes. If each crayon box has 12 crayons, how many crayon boxes can they make in 15 minutes?
  1.    750
  2.    800
  3.    900
  4.    1000
 Discuss Question
Answer: Option A. -> 750
:
A
Let n be the number of boxes.
As there are 12 crayons in each box, 2400 crayons fits into
240012=200boxes
Now the number of boxes produced will be directly proportional to time taken.
AB= Constant
A1B1 =A2B2
No.ofcrayonsboxestime=2004=n15
So, n = 750
Question 13. Working at the same constant rate, 7 identical machines can produce a total of 490 toys per minute.At this rate, how many toys could 10 such machines produce in 5 minutes?
  1.    2,700
  2.    3,500
  3.    4,200
  4.    4,500
 Discuss Question
Answer: Option B. -> 3,500
:
B
Let the required number of toys produced by 7 machines in 5 minutes be n.
As the time increases, the number of toys increases. Hence they are in direct proportion.
Working At The Same Constant Rate, 7 Identical Machines Can ...
n = 490 x 5= 2450
So, 7 machines can make 2,450 toys in 5 minutes.
As the number of machines increases, number of toys increases. They are in direct proportion.
Let k is thenumber of toys produced by 10 machines in 5 minutes.
Working At The Same Constant Rate, 7 Identical Machines Can ...
Then, k = 2450×107
k = 3500
So, the number of toys produced = 3,500
Question 14. 10 men can reap a field in 20 days. 10 men reaped the field for 10 days and after 10 days 10 more men join them. When will the work be finished?
  1.    15 days
  2.    25 days
  3.    30 days
  4.    12 days
 Discuss Question
Answer: Option A. -> 15 days
:
A
Total number of work days required =10 x 20 = 200
Since 10 men worked for 10 days, 10 x 10 = 100 days work is already done.
So, 200 - 100 = 100 days of work is left.
Once, 10 more men joined, total number of workers=20
So, number of days required more =10020=5
Thus, total number of days = 10 + 5 = 15.
Question 15. 4 oxen or 12 cows can graze a field in 32 days. How long would 7 oxen and 3 cows take to graze the same field?
  1.    12 days
  2.    17 days
  3.    32 days
  4.    16 days
 Discuss Question
Answer: Option D. -> 16 days
:
D
4 oxen = 12 cows
1 ox = 124 cows
7oxen124×7cows=21cows
(7 oxen + 3 cows) (21 cows + 3 cows) = 24 cows
Now, 12 cows can graze the field in 32 days.
So, 1 cow can graze the field in (32×12) days.
[less cows, more days]
24 cows can graze the field in 32×1224=16days
[more cows, less days]
Hence, 9 oxen and 3 cows can graze the field in 16 days
.
Question 16. I decided to purchase an anniversary gift for my parents. I selected gifts, 3 of which costs Rs.550. If I want to spend Rs.1100, I could purchase 6 gifts.
  1.    True
  2.    False
  3.    67 km
  4.    86 km
 Discuss Question
Answer: Option A. -> True
:
A
Numberofgifts3yPrice(InRupees)5501100
3550=y1100y=3×1100550=6gifts
Question 17. An army camp of 250 men has provision for 350 days. After 25 days, 50 men died due to epidemic. The food will last for 
___ days.
 Discuss Question

:
Remaining number of men = 250-50 =200 men
Remaining number of days = (350-25) days = 325 days.
250 men had provisions for 325 days
1 man had provisions for (250 × 325) days
200 men had provisions for (250×325)200 days


= 406.25days=406days
hence, the remaining food will last for 406 days.

Question 18. A bottle filling machine can fill 238 bottles in 2hrs. In 7hrs, it can fill 
___ bottles.
 Discuss Question

:
Numberofbottles238yTime(Inhours)27
The time taken and the number of bottles filled are directly proportional.
AB= Constant
A1B1 =A2B2
2238=7y
y=7×2382
y=833bottles
Question 19. Sophia was counting the number of crystals in 5kg of sugar. Can you help her to find the number of crystals in 5kg without actual counting, if 12kg of sugar contains 24 x 104 crystals?
  1.    2 x 104
  2.    1 × 105
  3.    2.4 x 106
  4.    24 x 102
 Discuss Question
Answer: Option B. -> 1 × 105
:
B
Weightofsugar125Numberofcrystals24×104y
This situation follows direct proportionality.
1224×104=5y
y=105
Question 20. Ipsa bought a car which covers 363 km in 24.2 litres of petrol. What will be the distance covered using 7 litres of petrol?
  1.    213 km
  2.    105 km
  3.    67 km
  4.    86 km
 Discuss Question
Answer: Option B. -> 105 km
:
B
Let the required distance be y.
Distance(inkm)363yAmountofpetrol(inl)24.27
The distance travelled and the amount of petrol consumed are directly proportional
AB= Constant
A1B1 =A2B2
Ipsa Bought A Car Which Covers 363 Km In 24.2 Litres Of Petr...
24.2363 =7y
24.2×y=363×7
y=7×36324.2=105 km

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