Question

Children's Day the students of Grade of a school decided to plant as many

saplings as the number of students in Grade 4000 saplings were bought by the

If after plantation 31 saplings were left how many students were there in

Answer 1

Answer:

According to the question , there are two sections of each class so the number of trees that are planted by students of class I, class II, class III, …..& class XII are:

Number of trees planted by the students of two sections of class I = 2× 2= 4

Number of trees planted by the students of two sections of class II = 2 × 4 = 8

Similarly,

Number of trees planted by the students of two sections of class 3 = 2 × 6 = 12

Number of trees planted by the students of two sections of class 12 = 2 × 24 = 48

So, the number of trees planted by the students of two sections of different classes are 4, 8, 12, …… 48

This series forms an AP

Here,first term( a) = 4, common Difference (d ) = 8 – 4 = 4, last term (l)= 48 and (number of terms)n = 12

Number of trees planted by the students = sum of 12 terms of above AP

Sn = n/2[a + l ],

Sn = 12/2[ 4 + 48]

Sn = 6 × 52 = 312

Hence, the total number of trees planted by the students is 312.