Five men working six hours a day take eight days to fill a trench. How long does it take 3 men working eight hours a day to fill the same trench.

The correct answer is 10 days.

Step-by-step explanation:

To fill a trench, 5 men work for 6 hours a day for eight days.

Total work hours required is given by 5 × 6 × 8 = 240 hours.

The same work is supposed to be done by 3 men working 8 hours a day.

Let these three men need to work for x days.

Therefore total work hour these group of three men gave = 3 × 8 × x = 24x hours

Therefore the work hour of both the group of 5 men and 3 men should be equal.

⇒ 24x = 240

⇒ x = 10

Therefore the group of 3 men have to work for 10 days to fill the trench.

answer: ratio of volume of cone (with 3 times the height and equal diameter) to volume of cylinder is 2 to 1. the value of π is not used.

step-by-step explanation:

radius is diameter/2 = 4.

area of circle is π r^2.

volume of cylinder is height × area of base = hπr^2 = 3(4^2) π = 48π cubic inches.

not knowing the formula for volume of cone, i calculate it using calculus (which is for calculating things).

volume of cone is integral 0 to h area(y) dy. area(y) is π r(y)^2. r(y) runs r to zero as y runs zero to h, r(0) = r, r(h) = 0.

r(y) = r - r/h y

area(y) = π (r - r/h y)^2 = π (r^2 - 2r^2y/h + r^2y^2/h^2) = π r^2(1-2y/h+y^2/h^2)

antiderivative area(y) = π r^2 (y-y^2/h+y^3/(3h^2))

integral 0 to h = π r^2(h-h^2/h+h^3/(3h^2) - (0)) = π r^2(h - h + h/3) = π r^2(h/3) = π/3 r^2 h

volume of this cone is π/3(4^2)18 cubic inches.

= 6 16 π = 96π cubic inches.

cone has twice the volume, 96/48.

cone height is 6 times the cylinder.

ratio of volume formula: π r^2 cancels.

cone over cylinder ratio is 6h/3 to h, 2 to 1.