help!! i really tried this.?

Question

a contractor undertakes to dig a canal, 6 km long, in 35 days and employed 90 men. he finds that after 20 days only 2 km of canal have been completed. how many more men must be employed to finish the work in time.l
ans150 men

12 typists, all working with same speed, type a certain no. of pages im 18 days working 8 hours a day. find, how many hours per day must 16 typists work in order to type the same no. of pages in 9 days?
ans12hours per day.

this is based on the unitary method.

Answer 1

1) Canal completed 2 km. Remained 6 - 2 = 4 km
Days completed = 20. Days left = 35 - 20 = 15
2 km of canal dug in 20 days by 90 men
Therefore, 1 km canal dug in 20 days by 90/2 men = 45 men
Therefore, 1 km canal dug in 1 day by 45*20 men
Therefore, 4 km canal dug in 1 day by 45*20*4 men
Therefore, 4 km canal dug in 15 days by (45*20*4)/15 men
= 240 men
But he has only 90 men. So he needs another 240 - 90 = 150 men

2)12 typists complete in 18 days at 8 hours per day
Therefore 1 typist completes in 18 days at 8*12 hours per day
Therefore 1 typist completes in 1 day at 8*12*18 hours per day
Therefore 16 typists complete in 1 day at (8*12*18)/16 hours per day
Therefore 16 typists complete in 9 day at (8*12*18)/(16*9) hours per day = 12 hours per day.

Answer 2

150 MEN. This allowing for 15 mins. tea breaks and a stat 8 hour day. You could shorten thi somewhat and save money on Labour. Work the front men in a diagonial line from A to B. using "X" as the return point. When your 2 front men have reached the "X" Point, then replace them with 2 from the rear. By the time you have created a circle, you will have dug the canal in record time. A BIG SAVING.

Answer 3

present digging capacity is 1/3 canal in 20 days. needed capacity is 2/3 canal in 15 days. manpower should be increased by 2/3*4=8/3. available manpower 60, required manpower 60*8/3=160.
typing - present man hours is 12*18*8
needed man hours is 16*9*X = 12*18*8
x = hours per day
x=12*18*8/16/9 = 12

Answer 4

A)
If 90 men dig 2km in 20 days then that's 0.1km per day and 0.1/90 = 0.0011km per man per day

They have 15 days left to finish 4km so 4km/15days = 0.2666 km per day

0.2666km per day / 0.0011 km per man per day = 240 men.

We already have 90 men so we need to employ another 150.




B)
12 typists work 18 days at 8 hours a day... thats 12x18x8 = 1728 man days of work.

16 typists x 9days x ??hours a day = 1728

1728 / 16 / 9 = 12 hours a day.

Answer 5

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Answer 6

ummmmmm.....I don't know.