Question

months of mass Mr can we spent Rupees 1 on the first day ,rupees 3 on the second day, 5 on the third day and so on .what is his total expenditure for the whole month ?​

Answer 1

Answer:

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.

Explanation:

let n = 29 days  

d =common difference

let s = saving

s=n/2 (2a+(n-1)*2)

s=29/2(2*2+(29-1)*2)

s=29/2(4+28*2)

s=29/2(56+4)

s=29*2*60

s=29*30

s=870

value dipicted is economy