There are 12 saplings to be planted in a straight line at an interval of 10 m between two consecutive saplings Jeremey can carry only 1 sapling at a time and he has to come back to the original point to take the next sapling He plants 12 saplings in this manner planting the first sapling at the original point After planting the saplings he comes back to the original point In the process what is the total distance Jeremey covers ?

Dear Student,

For sapling 1, no distance is covered as she planted it at original point and hence no return distance.For sapling 2, distance covered=10 mReturn distance=10 mFor sapling 3, distance covered=20 mReturn distance=20 mand so onThus the distances covered for saplings can be represented as:0,2(10),2(20),...i.e. 0,20, 40,...It represents an A.P. with first term 0 and common difference 20.Therefore total distance covered by Jeremey for planting 12 saplings and coming back to original position=S12=12220+12-120=61120=1320 m

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  • 4
Jeremy has to come back after planting every seed, Hence, every journey counts twice, 2( 10 + 20 + 30+ 40 + 50 + 60 + 17 + 80 + 90+ 100 + 110 + 120)
  • 0
Sn = n/2 × ( a + l ) = 12/2 × (10 + 120) =6 × 130 = 780 m As Jeremy covers all distances twice, = 780 × 2 = 1560m
  • -1
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