⁞ Chain Rule
Aptitude ➤ Chain Rule ➤ 1
Question 11
Q11. If the cost of printing a book of 320 leaves with 21 lines on each page and on an average 11 words in each line is Rs. 19, find the cost of printing a book with 297 leaves, 28 lines on each page and 10 words in each line.
Answer : 21 3⁄8
Let the required cost be Rs. x. Then ,
∴ 320 × 21 × 11 × x = 297 × 28 × 10 × 19
⇒ x = 171/8
= Rs. 21 3⁄8
⚔ DISCUSS
Question 12
Q12. If 80 lamps can be lighted, 5 hours per day for 10 days for Rs. 21.25, then the number of lamps, which can be lighted 4 hours daily for 30 days, for Rs. 76.50, is :
Answer : 120
Let the required number of lamps be x. Then ,
∴ 4 × 21.25 × 30 × x = 5 × 76.50 × 10 × 80
⇒ x = 120
Hence, the required number of lamps is 120.
⚔ DISCUSS
Question 13
Q13. If 9 engines consume 24 metric tonnes of coal, when each is working 8 hours day, how much coal will be required for 8 engines, each running 13 hours a day, it being given that 3 engines of former type consume as much as 4 engines of latter type?
Answer : 26
Let 3 engines of former type consume 1 unit in 1 hour.
Then, 4 engines of latter type consume 1 unit in 1 hour.
∴ 1 engine of former type consumes (1/3) unit in 1 hour.
1 engine of latter type consumes (1/4) unit in 1 hour.
Let the required consumption of coal be x units.Then ,
∴ 9 × 8 × (1/3) × x = 8 × 13 × (1/4) × 24
⇒ x = 624/24 = 26
Hence, the required consumption of coal = 26 metric tonnes.
⚔ DISCUSS
Question 14
Q14. 15 men take 21 days of 8 hours each to do a piece of work. How many days of 6 hours each would 21 women take, if 3 women do as much work as 2 men ?
Answer : 30
3 women ≡ 2 men
So, 21 women ≡ 14 men .
Let the required number of days be x. Then ,
∴ 14 × 6 × x = 15 × 8 × 21
⇒ x = (15 × 8 × 21)/(14 × 6) = 30
Hence, the required number of days is 30.
⚔ DISCUSS
Question 15
Q15. If 3 men or 6 boys can do a piece of work in 10 days, working 7 hours a day; how many will it take to complete a piece of work twice as large with 6 men and 2 boys working together for 8 hours a day ?
Answer : 7.5
3 men ≡ 6 boys
⇒ 6 men + 2 boys ≡ 14 boys
Let the required number of days be x. Then ,
∴ 1 × 14 × 8 × x = 2 × 6 × 7 × 10
⇒ x = 840/112 = 7.5
Hence, the required number of days is 7.5 days.
⚔ DISCUSS
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