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Doubt
Thirty trees are planted in a straight line at intervals of 5 m. To water them the gardener needs to bring water for
each three separately from a well, which is 10 m from the first tree in line with the trees. How far will be have to walk
in order to water all the trees, beginning with the first tree? Assume that he starts from the well.
1)
4, 785 m
2)
4, 795 m
3)
4, 800 m
4)
4, 810 m
5)
None of these
Answer Explanation
Since the gardener starts from the well
Therefore , Distance covered by gardener for water
to first tree D1 = 0A1 = 10 metre
Distance covered by gardener for water to second
tree D2 = A10 + 0A2
= 10 + 15 = 25 metre
Distance covered by
gardener for water to third eye D3 = A20 + 0A3
= 15 + 20
=35 metre
Distance covered by gardener for water to fourth
tree D4 = A30 + 0A4
Distance covered by gardener for water to all the
trees
Answers (1)
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Since the gardener starts from the well
Therefore , Distance covered by gardener for water
to first tree D1 = 0A1 = 10 metre
Distance covered by gardener for water to second
tree D2 = A10 + 0A2
= 10 + 15 = 25 metre
Distance covered by
gardener for water to third eye D3 = A20 + 0A3
= 15 + 20
=35 metre
Distance covered by gardener for water to fourth
tree D4 = A30 + 0A4
Distance covered by gardener for water to all the
trees
D = 10 + 25 + 35 +
45 + …..to 30 terms
= 10 + ( 25 + 35 +
45 + …to 29 terms)
= 10 + 29 / 2 {
2.25 + (29 – 1)10 }
= 10 + 29 / 2 { 50 +
280}
= 10 + 29 / 2 x 330
= 10 + 4785
= 4795 metre
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