13. Anuj gets pocket money from his father every day. Out of the pocket money, he saves Rs 2.75 on first day, Rs 3 on second day, Rs 3.25 on third day and so on. On the basis of above information, answer the following questions. (a) what is the total amount saved by Anuj in 8 day? (b) On which day, he save ten times as much as he saved on day-1 ?​

Answers 1

Answer:

Step-by-step explanation:

We can consider the following situation in the form of an Arithmetic Progression.

a = 2.75 , d = 0.25 ( 3 - 2.75 )

AP = 2.75 , 3 , 3.25 , 3.5 ......

(i) Total amount saved in 8 days = Sum of the first 8 terms of the above AP

N = No.of terms .

[tex]S_{n} = N/2 \ ( 2a + (n-1) d ) \\\\S_{8} = 8/2 \ (2(2.5) + (8-1)0.25)\\ \\S_{8} = 4 \ ( 5 + 7(0.25) )\\\\S_{8} = 4 \ (5 + 1.75)\\\\S_{8} = 4 \ (6.75)\\\\S_{8} = 27[/tex]

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(b)

Amount saved on the first day = 2.75

Ten times the amount = 27.5

So,we have to find which term of the AP has the value 27.5.

We have to find N

[tex]a_{n} = a + (n-1)d\\\\27.5 = 2.75 + 0.25(n-1)\\ \\24.75 = 0.25(n-1) \\\\99 = n-1 \\\\n = 100[/tex]

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