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- Question
- Find the sum of first 84 even numbers
Options- A. 7140
- B. 7540
- C. 6720
- D. 8832
- Correct Answer
- 7140
ExplanationSum of first n even numbers = n( n +1 )
Given n = 84
? Required sum = 84 ( 84 + 1 )
= 84 x 85
= 7140 - 1. Find the sum of cube of first 15 natural numbers.
Options- A. 15400
- B. 14400
- C. 16800
- D. 13300 Discuss
- 2. Find the sum of square of first 35 natural numbers.
Options- A. 14910
- B. 15510
- C. 14510
- D. 16510 Discuss
- 3. Find the sum of first 25 natural numbers.
Options- A. 432
- B. 315
- C. 325
- D. 335 Discuss
- 4. 7 6n - 6 6n, where n is an integer greater than 0, is divisible by
Options- A. 13
- B. 127
- C. 559
- D. None of these Discuss
- 5. If n is any odd number greater than 1, then n( n 2 -1 ) is
Options- A. divisible by 96 always
- B. divisible by 48 always
- C. divisible by 24 always
- D. None of these Discuss
- 6. Find the sum of first 37 odd numbers
Options- A. 1369
- B. 1295
- C. 1388
- D. 1875 Discuss
- 7. Sum of first 15 multiple of 8 is
Options- A. 960
- B. 660
- C. 1200
- D. 1060 Discuss
- 8. What is the unit digit in the ( 6817 ) 754?
Options- A. 8
- B. 4
- C. 2
- D. 9 Discuss
- 9. What is th unit digit in ( 3 65+6 59+7 71 )?
Options- A. 6
- B. 4
- C. 2
- D. 1 Discuss
- 10. A number divided by 56 gives 29 as remainder. If the same number is divided by 8, the remainder will be ..
Options- A. 4
- B. 5
- C. 6
- D. 7 Discuss
Number System problems
Search Results
Correct Answer: 14400
Explanation:
Sum of cubes of first n natural numbers = [ n(n+1) ]2
Given n = 15
? Required sum = [ ( 15 x 16 ) / 2 ] 2
= (15 x 8 )2
= 1202
= 14400
Correct Answer: 14910
Explanation:
Sum of the square of first n natural numbers = n(n+1)(2n+1) / 6
Given n = 35
? Required sum = ( 35 x 36 x 71 ) / 6
= 14910
Correct Answer: 325
Explanation:
Sum of first n natural numbers = n(n+1)/2
= 25 ( 25 + 1 ) / 2
= ( 25 x 26 ) / 2
= 325
Correct Answer: 127
Explanation:
For n =1
76n - 66n = 76 - 66
? ( 73 )2 - ( 63 )2
? ( 73 - 63 )( 73 + 63 )
= ( 343 - 216 )( 343 + 216 )
= 127 x 559
? it is clearly divisible by 127.
Correct Answer: divisible by 24 always
Explanation:
Solving the question by taking two odd numbers greater than 1 i.e. 3 and 5,
for n =3, n( n2 -1 ) = 3( 9 - 1) = 24
for n = 5 n( n2 -1 ) = 5( 25 - 1) = 120
Using option we find that both the number are divisible by 24.
Correct Answer: 1369
Explanation:
Sum of first n odd number = n2
Given, n = 37
? Required sum = 372
= 37 x 37
= 1369
Correct Answer: 960
Explanation:
First 15 multiple of 8 are 8, 16, 24, ......, 120
Sum = 8 (1 + 2 + 3 + 4 ......+ 15)
= 8 [ n(n + 1) / 2]
= 8 x 15 x 8
960
Correct Answer: 9
Explanation:
Required unique digit = Unique digit in (7)754
= Unique digit in { (74)188 x 72 }
= Unique digit in ( 1 x 49 ) = 9
Correct Answer: 4
Explanation:
Unit digit in 34 = 1
? Unit digit in ( 34 )16 = 1
? Unit digit in 365 = 3
Unit digit in 659 = 6
Unit digit in 771 = 3
? Required unit digit = Unit digit in ( 3 x 6 x 3 )
= Unit digit in 54
= 4
Correct Answer: 5
Explanation:
Let the number be N
According to question
N = 56k + 29
Then,
N = ( 8 x 7k ) + ( 8 x 3 ) + 5
Therefore if N will be divided by 8 the required remainder will = 5
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