Question

If it takes 6 men 4h to dig a hole 6m deep,how long will it take 10 men to dig a hole 5m deep?

Answer 1

6 men --- 4 hrs --- 6m deep
1 man ---24 hrs --- 6m deep
10 men 24/10 hrs -- 6 m deep
10 men 2.4 hrs --- 6 m deep
10 men 2.4/6 hrs --1 m deep
10 men .4 hrs ===1 m deep
10 men .4(5) hrs --- 5 m deep

10 men 2 hrs ---- 5 m deep

OR

it takes 24 manhrs to dig a 6 m deep hole
it takes 4 manhrs to dig a 1 m deep hole
it takes 20 manhrs to dig a 5 m deep hole
so it takes 10 men 2 hrs to dig a 5 m deep hole

Answer 2

Thank you very much!!!

then how to do this qn?

y is directly proportional to the square root of x.If y is quadrupled,find the percentage change in x.

Answer 3

y1/y2 = √x1/√x2

1/4 = √x1/√x2
√x2 = 4√x1
square both sides
x2 = 16x1
x2/x1 = 16/1 or 1600 %

e.g. suppose x = 36
then y = 6
now we want y to be quadrupled, so y = 24
and x would be such that
√x = 24 , so x = 576
percentage increase in x = 576/36 = 16
so 16 fold increase is 1600%