25 trees are planted in a straight line 5 metre apart from each other. To water them the gardener must bring water for each tree separately from a well 10 metre from the first tree in line with the trees. The distance he will move in order to water all the trees beginning with the first if he starts from the well is :

Explanation

Total distance that the gardener need to move to water all the trees will be given by,` S = 2 ( 10 + ( 10 + 5 ) + ( 10 + 10 ) + ( 10 + 15 ) + ... ( 10 + 5 ( 24 ) ) − ( 10 + 5 ( 24 ) ) `


`S = 2 ( 10 + 15 + 20 + ... + 130 ) − 130 `


`=>S=2(10+15+20+...+130)-130`


Sum of AP, `S_m = (a + l)/2 ⋅ n`


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