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Which of the following is a prime number

  • 9
  • 2
  • 4
  • 8

Answer: Option B

Explanation:

A prime number is a natural number greater than 1 which has no positive divisors other than 1 or itself.
So from above options 2 is that number

Similar Questions :

1. \begin{aligned}
46^2 - (?)^2 = 4398 - 3066
\end{aligned}

  • 23
  • 18
  • 38
  • 28

Answer: Option D

2. Simplify 586645 * 9999

  • 5865863355
  • 5665863355
  • 4865863355
  • 4665863355

Answer: Option A

Explanation:

Although it is a simple question, but the trick is to save time in solving this.
Rather than multiplying it we can do as follows:
586645 * (10000 - 1) = 5866450000 - 586645 = 5865863355

3. A number when divided by 44, gives 432 as quotient and 0 as remainder. What will be the remainder when dividing the same number by 31

  • 5
  • 3
  • 4
  • 6

Answer: Option A

Explanation:

P ÷ 44 = 432

=> P = 432 * 44 = 19008

P / 31 = 19008 / 31 = 613, remainder = 5

4. What least value should be replaced by * in 223*431 so the number become divisible by 9

  • 3
  • 4
  • 5
  • 6

Answer: Option A

Explanation:

Trick: Number is divisible by 9, if sum of all digits is divisible by 9, so (2+2+3+*+4+3+1) = 15+* should be divisible by 9,
15+3 will be divisible by 9,
so that least number is 3.

5. 1939392 * 625

  • 1212120010
  • 1212120000
  • 1212120011
  • 1212121010

Answer: Option B

Explanation:

Trick: when multiplying with \begin{aligned} 5^n
\end{aligned} then put n zeros to the right of multiplicand and divide the number with \begin{aligned} 2^n
\end{aligned}
So using this we can solve this question in much less
time.
\begin{aligned} 1939392 \times 5^4 = \frac {19393920000}{16} = 1212120000
\end{aligned}

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