Four gardeners with four grass mowers mow 400 sq. m of ground in 4 hours. How long would it take for eight gardeners with eight grassmowers to mow 800 sq.m of the ground?

Question: Four gardeners with four grassmowers mow 400 sq. m of ground in 4 hours. How long would it take for eight gardeners with eight grass mowers to mow 800 sq. m of the ground?

Solution:
Since each gardener would work with one grassmower,
So, we shall consider 1 gardener and 1 grass mower as one unit.
Let the required time be x hours

ATQ,
8 × 400 × x = 4 × 800 × 4
⇒ x = (4 × 800 × 4)/(8 × 400)
∴ x = 4 hours