Question 18

Find the sum to *n* terms of the sequence, 8, 88, 888, 8888…

Answer

The given sequence is 8, 88, 888, 8888…

This sequence is not a G.P. However, it can be changed to G.P. by writing the terms as

*S*_{n} = 8 + 88 + 888 + 8888 + …………….. to *n* terms

- Q:-
Find the sum of integers from 1 to 100 that are divisible by 2 or 5.

- Q:-
If the sum of three numbers in A.P., is 24 and their product is 440, find the numbers.

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A wheel makes 360 revolutions in one minute. Through how many radians does it turn in one second?

- Q:- Find the sum of all natural numbers lying between 100 and 1000, which are multiples of 5.
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The sum of the first four terms of an A.P. is 56. The sum of the last four terms is 112. If its first term is 11, then find the number of terms.

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^{2}, 3^{3}, … are needed to give the sum 120? - Q:-
Find the sum of all numbers between 200 and 400 which are divisible by 7.

- Q:- Write the following sets in roster form:

(i) A = {x: x is an integer and - 3 < x < 7}.

(ii) B = {x: x is a natural number less than 6}.

(iii) C = {x: x is a two-digit natural number such that the sum of its digits is 8}

(iv) D = {x: x is a prime number which is divisor of 60}.

(v) E = The set of all letters in the word TRIGONOMETRY.

(vi) F = The set of all letters in the word BETTER. - Q:-
Insert five numbers between 8 and 26 such that the resulting sequence is an A.P.

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Find the sum of all two digit numbers which when divided by 4, yields 1 as remainder.

- Q:- Find the sum to n terms of the A.P., whose kth term is 5k + 1.
- Q:-
How many 3-digit even numbers can be formed from the digits 1, 2, 3, 4, 5, 6 if the digits can be repeated?

- Q:- Find the sum of all natural numbers lying between 100 and 1000, which are multiples of 5.
- Q:-
Find the sum of integers from 1 to 100 that are divisible by 2 or 5.

- Q:-
An experiment consists of rolling a die and then tossing a coin once if the number on the die is even. If the number on the die is odd, the coin is tossed twice. Write the sample space for this experiment.

- Q:-
Find the sum of all two digit numbers which when divided by 4, yields 1 as remainder.

- Q:- In an A.P., if pth term is \begin{align} \frac{1}{q} \; and \;qth\; term \; is\; \frac{1}{p}\end{align} , prove that the sum of first pq terms is \begin{align} \frac{1}{2}(pq+1) \; where \; p ≠ q \end{align}
- Q:-
The sum of first three terms of a G.P. is and their product is 1. Find the common ratio and the terms.

- Q:-
A point is in the XZ-plane. What can you say about its

*y*-coordinate? - Q:-
A man starts repaying a loan as first installment of Rs. 100. If he increases the installment by Rs 5 every month, what amount he will pay in the 30th installment?

ayush
2019-03-07 15:42:36

thanks lord

ayush
2019-03-07 15:42:19

thanks lord

ABHISHEK ANAND
2018-03-31 17:26:57

what will be the answer if sum of infinity term are asked.

Sup
2017-02-15 07:35:27

TQ very very much

Amrith
2016-10-04 20:52:22

Thank you very muchðð

- NCERT Chapter