This is the basic and conceptual question from Chapter name- Arithmetic Progression
Chapter number- 9
Exercise 9.6
In this question we have been given that Ramkali would need Rs. 1800 for admission fee and books etc.,for her daughter to start going to school from the next year.
She saved Rs. 50 in the first month of this year and increased her monthly saving by Rs. 20.
Now we have to find that after a year, how much money will she save
Also we have to find out if she will be able to fulfill her dream of sending her daughter to school.
CBSE DHANPAT RAI publications
Class:- 10th
Solutions of CBSE Mathematics
Question 62
Given that Ramkali has saved in following sequence in a year(every month record): 50, 70, 90,. . . .
First term(a) = 50 and common difference(d) = 20.
Now by using the formula of the sum of n terms of an A.P.
Sn = n[2a +(n – 1)d] / 2
So,
Now, sum of the savings after 1 year(12 months) would be S12 as value of n in this case is 12.
S12 = 12[2(50) + (12 – 1)20] / 2
= 6[100 + 220]
= 6[320]
= 1920
Hence, Resham would save Rs 1920 by the end of 1 year(12 months) which is
greater than Rs 1800, she would be able to fulfill her dream of sending her daughter to school.