Advertisements
Advertisements
प्रश्न
In a ‘Mahila Bachat Gat’, Kavita invested from the first day of month ₹ 20 on first day, ₹ 40 on second day and ₹ 60 on third day. If she saves like this, then what would be her total savings in the month of February 2020?
Advertisements
उत्तर
2020 is a leap year.
In February month there are 29 days.
n = 29
On the first day of the month Kavita invested ₹20.
On the second day, she invested ₹40.
On the third day, she invested ₹60.
Kavita's investment is in A.P. 20, 40, 60, ....
a = 20, n = 29, d = 20
Now, `S_n = n/2 [2a + (n - 1)d]`
∴ `S_29 = 29/2 [2(20) + (29 - 1)(20)]`
= `29/2 [40 + 28 xx 20]`
= `29/2 [40 + 560]`
= `29/2 [600]`
= 29 × 300
= 8700
∴ Total savings of Kavita in the month of February 2020 is ₹ 8,700.
APPEARS IN
संबंधित प्रश्न
Find the sum of first 51 terms of an AP whose second and third terms are 14 and 18 respectively.
Find the sum of all 3 – digit natural numbers which are divisible by 13.
Find the sum of all natural numbers between 250 and 1000 which are divisible by 9.
In an A.P. the first term is 25, nth term is –17 and the sum of n terms is 132. Find n and the common difference.
The sum of n natural numbers is 5n2 + 4n. Find its 8th term.
The 8th term of an AP is zero. Prove that its 38th term is triple its 18th term.
The sum of first seven terms of an A.P. is 182. If its 4th and the 17th terms are in the ratio 1 : 5, find the A.P.
The sum of first n terms of an A.P is 5n2 + 3n. If its mth term is 168, find the value of m. Also, find the 20th term of this A.P.
Q.6
Q.2
