Advertisements
Advertisements
प्रश्न
If the common differences of an A.P. is 3, then a20 − a15 is
विकल्प
A. 5
B. 3
C. 15
D. 20
उत्तर
Let the first term of the A.P. be a.
`a_n=a(n-1)d`
`a_20-a_15=[a+(20-1)d]-[a+(15-1)d]`
`=19d-14b`
`=5d`
`=5xx3`
`=15`
The correct answer is C.
APPEARS IN
संबंधित प्रश्न
The first and the last terms of an AP are 8 and 65 respectively. If the sum of all its terms is 730, find its common difference.
In an AP, given a = 7, a13 = 35, find d and S13.
In an A.P., the sum of first n terms is `(3n^2)/2 + 13/2 n`. Find its 25th term.
In a flower bed, there are 43 rose plants in the first row, 41 in second, 39 in the third, and so on. There are 11 rose plants in the last row. How many rows are there in the flower bed?
Find the first term and common difference for the A.P.
127, 135, 143, 151,...
Find out the sum of all natural numbers between 1 and 145 which are divisible by 4.
Write the value of a30 − a10 for the A.P. 4, 9, 14, 19, ....
Obtain the sum of the first 56 terms of an A.P. whose 18th and 39th terms are 52 and 148 respectively.
The first term of an AP is –5 and the last term is 45. If the sum of the terms of the AP is 120, then find the number of terms and the common difference.
In an AP, if Sn = n(4n + 1), find the AP.
