# Number System Aptitude Questions and Answers:

#### Overview:

 Questions and Answers Type: MCQ (Multiple Choice Questions). Main Topic: Quantitative Aptitude. Quantitative Aptitude Sub-topic: Number System Aptitude Questions and Answers. Number of Questions: 10 Questions with Solutions.

1. Find the sum of prime numbers lying between 50 to 80?

1. 460
2. 490
3. 520
4. 530

Solution: Prime numbers lying between 50 to 80 are 53, 57, 59, 61, 67, 71, 73, 79.

Now the sum of these numbers $$53 + 57 + 59 + 61 + 67 + 71 + 73 + 79$$ $$= 520$$ Hence the sum of prime numbers lying between 50 to 80 is 520.

1. There are four prime numbers written in ascending order. The product of the first three prime numbers is 230 and that of the last three is 530. Find the last prime number?

1. 47
2. 53
3. 57
4. 61

Solution: Let four prime numbers are A, B, C, and D then according to the question $$A \times B \times C = 230.....(1)$$ $$B \times C \times D = 530.....(2)$$ By dividing the equation (2) from equation (1) $$\frac{B \times C \times D}{A \times B \times C} = \frac{530}{230}$$ $$\frac{D}{A} = \frac{53}{23}$$ Hence the last number is 53.

1. The sum of the first 20 natural numbers is?

1. 210
2. 220
3. 225
4. 230

Solution: The sum of n natural numbers $$= \frac{n \ (n + 1)}{2}$$ The sum of 20 natural numbers $$= \frac{20 \ (20 + 1)}{2}$$ $$= \frac{20 \times 21}{2}$$ $$= 210$$

1. In a sum involving division, the divisor is 10 times the quotient and 4 times the remainder. If the remainder is 30 then find the dividend?

1. 1400
2. 1420
3. 1450
4. 1470

Solution: According to the question $$divisor = 10 \times quotient....(1)$$ $$divisor = 4 \times remainder$$ $$divisor = 4 \times 30$$ $$divisor = 120$$ by putting the value of divisor in equation (1) $$120 = 10 \times quotient$$ $$quotient = \frac{120}{10} = 12$$ Now $$dividend = divisor \times quotient \\ + remainder$$ $$= 120 \times 12 + 30$$ $$= 1440 + 30$$ $$dividend = 1470$$

1. If a number when divided by the sum of 220 and 120 gives two times their difference as quotient and 25 as the remainder then find the number?

1. 68025
2. 60050
3. 65022
4. 67035

Solution: According to the question $$divisor = 220 + 120 = 340$$ $$quotient = 2 \times (220 - 120)$$ $$= 2 \times 100 = 200$$ $$remainder = 25$$ Now $$dividend = divisor \times quotient \\ + remainder$$ $$= 340 \times 200 + 25$$ $$= 68000 + 25$$ $$= 68025$$