Q12 of 110 Page 41

A man has saved ₹640 during the first month, ₹720 in the second month and ₹800 in the third month. If he continues his savings in this sequence, what will be his savings in the 25th month?

The savings form the A.P.: 640, 720, 800 …


Here, first term, a = 640


We know that common difference, d = a1 – a.


∴ d = 720 – 640 = 80


We know that nth term of A.P. , tn = a + (n – 1) d.


⇒ t25 = 640 + (25 – 1) (80)


= 640 + (24) (80)


= 640 + 1920


= 2560


∴ The man’s savings in the 25th month are Rs. 2560.


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