Advertisements
Advertisements
प्रश्न
How many two-digits numbers are divisible by 3?
उत्तर
The two-digit numbers divisible by 3 are 12, 15, 18, ..., 99.
Clearly, these number are in AP.
Here, a = 12 and d =15 - 12 = 3
Let this AP contains n terms. Then,
an = 99
⇒ 12 + (n-1) × 3 =99 [an = a + (n-1) d]
⇒ 3n + 9 =99
⇒ 3n = 99 - 9 = 90
⇒ n = 30
Hence, there are 30 two-digit numbers divisible by 3.
संबंधित प्रश्न
How many terms of the A.P. 65, 60, 55, .... be taken so that their sum is zero?
In an AP given d = 5, S9 = 75, find a and a9.
In an A.P., if the 5th and 12th terms are 30 and 65 respectively, what is the sum of first 20 terms?
Find the sum of the first 15 terms of each of the following sequences having the nth term as
yn = 9 − 5n
Find the sum of first 12 natural numbers each of which is a multiple of 7.
What is the sum of first n terms of the AP a, 3a, 5a, …..
The next term of the A.P. \[\sqrt{7}, \sqrt{28}, \sqrt{63}\] is ______.
Write the nth term of an A.P. the sum of whose n terms is Sn.
If the first term of an A.P. is a and nth term is b, then its common difference is
Q.11
