model 6 operations of consecutive numbers (odd, even, square, etc.) Section-Wise Topic Notes With Detailed Explanation And Example Questions

MOST IMPORTANT quantitative aptitude - 6 EXERCISES

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The following question based on number system topic of quantitative aptitude

Questions : Two positive whole numbers are such that the sum of the first number and twice the second number is 8 and their difference is 2. The numbers are :

(a) 4,2

(b) 7,5

(c) 6,4

(d) 3,5

The correct answers to the above question in:

Answer: (a)

Let the numbers be x and y.

According to the question,

x + 2y = 8 .... (i)

x – y = 2 ....... (ii)

By equation (i) – (ii),

2y + y = 8 – 2

3y = 6; y = 2

From equation (ii),

x – 2 = 2 ; x = 4

Practice number system (model 6 operations of consecutive numbers (odd, even, square, etc.)) Online Quiz

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Read more operations on consecutive numbers Based Quantitative Aptitude Questions and Answers

Question : 1

What is the arithmetic mean of first 20 odd natural numbers ?

a) 22

b) 19

c) 17

d) 20

Answer: (d)

Sum of first n odd natural numbers = $n^2 = (20)^2$ = 400

Required average = $400/20$ = 20

Question : 2

The sum of three consecutive natural numbers each divisible by 5, is 225. The largest among them is

a) 70

b) 85

c) 75

d) 80

Answer: (d)

Let the required largest number be x.

According to the question,

x + x – 5 + x – 10 = 225

3x – 15 = 225

3x = 225 + 15 = 240

x = $240/3$ = 80

Question : 3

Find three consecutive numbers such that twice the first, three times the second and four times the third together make 191.

a) 20, 21, 22

b) 19, 20, 21

c) 21, 22, 23

d) 22, 23, 24

Answer: (a)

Numbers = x, x +1 and x + 2

2x + 3x + 3 + 4x + 8 = 191

9x = 191 – 11 = 180

x = 20

∴ Numbers = 20, 21 and 22

Question : 4

Which one of the following is a factor of the sum of first twentyfive natural numbers ?

a) 13

b) 26

c) 24

d) 12

Answer: (a)

1 + 2 + 3 + ... + n = ${n(n+1)}/2$

1 + 2 + 3 + .. + 25 = ${25(25 + 1)}/2$ = 25 × 13

Hence, 13 is a factor of required sum.

Question : 5

What is the sum of two consecutive even numbers, the difference of whose square is 84?

a) 42

b) 38

c) 34

d) 46

Answer: (a)

$(x + 2)^2 – x^2 = 84$

or $x^2 + 4x + 4 – x^2$ = 84

4x = 84 – 4 = 80

x = $80/4$ = 20

x + 2 = 20 + 2 = 22

∴ The required sum = 20 + 22 = 42

Question : 6

Find the sum of all positive multiples of 3 less than 50

a) 408

b) 400

c) 404

d) 412

Answer: (a)

Sum of all multiples of 3 upto 50

= 3 + 6 + ..... + 48

= 3 (1 + 2 + 3 + .... + 16)

= 3×${16(16+1)}/2$= 3 × ${272}/2$ = 408

[Since 1+2+3+…+n = ${n(n+1)}/2$]

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