6. Neela saves in a ‘Mahila Bachat gat’ Rs. 2 on the first day, Rs.4 on the second day, Rs. 6 on the third day and so on. What will be her saving in the month of February 2010 ?
Sol. The savings done by Neela on each day is as follows 2, 4, 6, .......
These every day savings form an A.P. with
First day saving (a) = 2
Difference in savings made in two successive days (d) = 2
Total no. of days in the month of February 2010 (n) = 28
∴ Total savings for the month of February (S28) = ?
Sn = n/2[2a + (n – 1) d]
∴ S28 = 28/2[2 (2) + (28 – 1) (2)]
∴ S28 = 14 [4 + 27 (2)]
∴ S28 = 14 [4 + 54]
∴ S28 = 14 [58]
∴ S28 = 812
∴ Neela saved Rs. 812 in the month of February.
