Question

In a school, tree planatation on Independence day was arranged. Every student from I standard will plant 2 trees, II standard students will plant 4 trees each, III standard students will plant 8 trees each etc. If there are 5 standard, how many trees are planted by the student of the school ?

• A. 62
• B. 25
• C. 54
• D. 15

Answer 1

The correct option is A 62

Number of tree planted by student from I standard$=2=2^1$
Number of tree planted by student from II standard$=4=2^2$
Number of tree planted by student from III standard$=8=2^3$
Number of tree planted by student from IV standard$=16=2^4$
Number of tree planted by student from V standard$=32=2^5$
Clearly it is an GP with first term $a=2$, common ratio $r=2$ and $n=5$
Therefore, total trees planted by all students$=S_5=\frac{a(r^5-1)}{r-1}=\frac{2(2^5-1)}{2-1}=2\times 31=62$