In a potato race 20 potatoes are placed in a line at intervals of 4 meters with the first potato 24 metres from the starting point. A contestant is required to bring the potatoes back to the starting place one at a time. How far would he run in bringing back all the potatoes ?
We have,
The distance travelled to bring the first potato, a2=2×24=48 m
The distance travelled to bring the second potato, a2=2×(24+4)=56 m
The distance travelled to bring the third potato, a3=2×(24+4+4)=64 m
As, a2−a1=56−48=8 and a3−a2=64−56=8
i.e., a2−a1=a3−a2
So, a1,a2,a3,…… are in A.P.
Also, a = 48, d = 8, n = 20
Now,
S20=202[2a+(20−1)d]
=10[2×48+19×8]
=10×(96+152)
=10×248=2480
So, he would have to run 2480 m to bring back all the potatoes.