Mahendra K. answered • 06/17/15

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A man can lay a concrete sidewalk in 5 days which means 1/5 sidewalk per day

Similarly, his assistant can lay same sidewalk in 8 days means 1/8 side walk per day.

Both of them working together will complete (1/5+1/8) = 13/40 side walk in a day

Both of them worked together for 2 days and completed 2*13/40 =26/ 40 side walk

After 2 days left over side walk is 1-26/40= 14/40

Days taken by Assistant to finish left over sidewalk is= (14/40) / (1/8)

=( 14*8) / (40*1) = 14/5= 2.8 days

The Assistant will finish leftover sidewalk in 2.8 days