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11. A flagstaff 17.5 m high casts a shadow of length 40.25 m. The height of the building, which casts a shadow of length 28.75 m under similar conditions will be:

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Solution:
Let the height of the building x metres.
Less lengthy shadow, Less in the height (Direct Proportion)
40.25:28.75::17.5:x40.25×x=28.75×17.5x=28.75×17.540.25x=12.5
12. In a camp, there is a meal for 120 men or 200 children. If 150 children have taken the meal, how many men will be catered to with remaining meal?

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Solution:
There is a meal for 200 children
150 children have taken the meal
Remaining meal is to be catered to 50 children
Now,
200 children = 120 men
∴ 50 children
=(120200×50)men=30 men
13. An industrial loom weaves 0.128 metres of cloth every second. Approximately, how many seconds will it take for the loom to weave 25 metres of cloth?

Discuss
Solution:
Le the required time be x seconds.
More metres, More time (Direct Proportion)
0.128:25::1:x0.128x=25×1x=250.128=25×1000128x=195.31
∴ Required time = 195 sec (approximately)
14. 36 men can complete a piece of work in 18 days. In how many days will 27 men complete the same work?

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Solution:
Let the required number of days be x.
Less men, More days (Indirect Proportion)
27:36::18:x27×x=36×18x=36×1827x=24
15. 4 mat-weavers can weave 4 mats in 4 days. At the same rate, how many mats would be woven by 8 mat-weavers in 8 days?

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Solution:
Let the required number of bottles be x.
More weavers, More mats (Direct Proportion)
More days, More mats (Direct Proportion)
Wavers4:8Days4:8}::4:x
4×4×x=8×8×4x=8×8×44×4x=16
16. The price of 357 mangoes is Rs. 1517.25. What will be the approximate price of 49 dozens of such mangoes ?

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Solution:
Let the required price be Rs. x
More mangoes, More price (Direct proportion)
357:(49×12)::1517.25:x357x=(49×12×1517.25)x=(49×12×1517.25)357x=2499
Hence, the approximate price is Rs. 2500
17. An industrial loom weaves 0.128 metres of cloth every second. Approximately, how many seconds will it take for the loom to weave 25 metres of cloth ?

Discuss
Solution:
Let the required time be x seconds
Then,
More metres, More time (direct proportion)
0.128:25::1:xx=250.128x=25×1000128x=195.31`
∴ Required time =195 seconds (approx)
18. A snapshot 178×212   is to be enlarged so that the longer dimension is 4. What will be the dimension of the shorter side ?

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Solution:
Let the dimension of the shorter side be x
More is the longer side, More is the shorter side (Direct proportion)
212:4::178:x52x=4×158x=(152×25)x=3
19. A canteen requires 651 bananas for a week. Totally, how many bananas will it require for the months of April, May and June ?

Discuss
Solution:
Total number of days = (30 + 31 + 30) = 91
Let the number of bananas be x
More days, More bananas (Direct proportion)
7:91::651:x7x=91×651x=(91×6517)x=8463
20. If 49 th of a bucket is filled in 1 minute, the rest of it will be filled in ?

Discuss
Solution:
Remaining part
=(149)=59 
Let the required time be x minutes
More volume to be filled , More time taken (Direct proportion)
 49:59::1:x49x=59x=(59×94)x=54