Advertisements
Advertisements
Question
If 45 persons can complete a work in 20 days, then the time taken by 75 persons will be ______ hours.
Advertisements
Solution
If 45 persons can complete a work in 20 days, then the time taken by 75 persons will be 288 hours.
Explanation:
∵ 45 persons can complete a work in 20 days.
∴ 1 person can complete a work in 45 × 20 i.e. 900 days.
Similarly, 75 persons can complete the same work in `900/75` = 12 days
= 12 × 24 ...[∵ 1 day = 24 h]
= 288 h
APPEARS IN
RELATED QUESTIONS
Which of the following quantities vary directly with each other?
(i) Number of articles (x) and their price (y).
(ii) Weight of articles (x) and their cost (y).
(iii) Distance x and time y, speed remaining the same.
(iv) Wages (y) and number of hours (x) of work.
(v) Speed (x) and time (y) (distance covered remaining the same).
(vi) Area of a land (x) and its cost (y).
The amount of extension in an elastic string varies directly as the weight hung on it. If a weight of 150 gm produces an extension of 2.9 cm, then what weight would produce an extension of 17.4 cm?
Two taps A and B can fill an overhead tank in 10 hours and 15 hours respectively. Both the taps are opened for 4 hours and they B is turned off. How much time will A take to fill the remaining tank?
A pipe can fill a cistern in 10 hours. Due to a leak in the bottom it is filled in 12 hours. When the cistern is full, in how much time will it be emptied by the leak?
When two quantities x and y are in ______ proportion or vary ______ they are written as `x oo y`.
The perimeter of a circle and its diameter vary ______ with each other.
The area of cultivated land and the crop harvested is a case of direct proportion.
A swimming pool can be filled in 4 hours by 8 pumps of the same type. How many such pumps are required if the pool is to be filled in `2 2/3` hours?
Match each of the entries in Column I with the appropriate entry in Column II
| Column I | Column II |
| 1. x and y vary inversely to each other | A. `x/y` = Constant |
| 2. Mathematical representation of inverse variation of quantities p and q |
B. y will increase in proportion |
| 3. Mathematical representation of direct variation of quantities m and n |
C. xy = Constant |
| 4. When x = 5, y = 2.5 and when y = 5, x = 10 | D. `p oo 1/q` |
| 5. When x = 10, y = 5 and when x = 20, y = 2.5 | E. y will decrease in proportion |
| 6. x and y vary directly with each other | F. x and y are directly proportional |
| 7. If x and y vary inversely then on decreasing x | G. `m oo n` |
| 8. If x and y vary directly then on decreasing x | H. x and y vary inversely |
| I. `p oo q` | |
| J. `m oo 1/n` |
A water tank casts a shadow 21 m long. A tree of height 9.5 m casts a shadow 8 m long at the same time. The lengths of the shadows are directly proportional to their heights. Find the height of the tank.

