Management Aptitude Test 2017 Paper

(d) 12
Let there are (n + 1) saplings planted in the process

Now, total distance covered by forester = 1.32 km = 1320 m
According to the question
, (10 + 10) + (20 + 20) + (30 + 30) ... = 1320 m
⇒ 20 + 40 + 60 + ... n = 1320
This forms an AP where a = 20, d = 40 - 20 = 20
${\mathit{S}}_{\mathit{n}}=\frac{\mathit{n}}{2}$[2a + (n - 1)d]
⇒ $\frac{\mathit{n}}{2}$[40 + (n - 1) 20] = 1320
⇒ 40n + 20n(n - 1) = 2640
⇒ ${\mathit{n}}^2$ + n -132= 0
⇒ ${\mathit{n}}^2$ + 12n - 11n - 132 = 0
⇒ (n - 11)(n + 12) = 0
⇒ n = 11, -12
(- ve value is not possible)
∴n = 11
Hence, there are n + 1 = 12 saplings planted.