A boy spends ₹ 10 on first day, ₹ 20 on second day, ₹ 40 on third day and so on. Find how much in all, will he spend in 12 days?

A geometric progression has common ratio = 3 and last term = 486. If the sum of its terms is 728; find its first term.

Find the sum of G.P. : 3, 6, 12, ……., 1536.