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 ?


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.