Ratios and Proportions (114 Questions with Explanation)

Basic Computer Knowledge Test Questions and Answers

1.

Find the fourth proportional to 2.4, 4.6 and 7.6? 

   A.) 14
   B.) 14.657
   C.) 15.56
   D.) 14.56

Answer: Option 'D'

Formula = Fourth propotional = (b × c)/a 
A = 2.4 , B = 4.6 and C = 7.6 
(4.6 × 7.6)/2.4 = 14.56

Basic Computer Knowledge Test Questions and Answers

2.

Find the third proportional to 9 and 12? 

   A.) 9
   B.) 108
   C.) 16
   D.) 9

Answer: Option 'C'

Formula = Third proportional = (b × b)/a 
A = 9 and B = 12 
(12 × 12)/ 9 = 144/9 = 16

Basic Computer Knowledge Test Questions and Answers

3.

Find the mean proportional between 49 & 81? 

   A.) 16
   B.) 10
   C.) 63
   D.) 12

Answer: Option 'C'

Formula = √a×b
A = 49 and B = 81 
√49×81 = 7 × 9 = 63

Basic Computer Knowledge Test Questions and Answers

4.

Find the fourth proportional to 0.2,0.12 and 0.3? 

   A.) 0.13
   B.) 0.18
   C.) 0.8
   D.) 0.15

Answer: Option 'B'

Formula = Fourth propotional = (b × c)/a 
A = 0.2 , B = 0.12 and C = 0.3 
(0.12 × 0.3)/0.2 
0.036/0.2 = 0.18

Basic Computer Knowledge Test Questions and Answers

5.

If a:b=1:2 and b:c=3:4 find a:b:c? 

   A.) 3:8:6
   B.) 3:12:6
   C.) 3:6:8
   D.) 1:2:4

Answer: Option 'C'

a:b = 1:2, b:c = 3:4 
1:2 
3:4 
(a = 1 × 3 = 3, b = 2 × 3 = 6 and c = 2 × 4 = 8)
(a = a × b, b = b × b and c = b × c) 
a:b:c = 3:6:8 

Basic Computer Knowledge Test Questions and Answers

6.

If a:b=1:2, b:c=3:4 and c:d = 2:3 find a:b:c:d? 

   A.) 3:6:8:24
   B.) 6:12:16:24
   C.) 6:18:24:16
   D.) 3:6:2:3

Answer: Option 'B'

a:b = 1:2, b:c = 3:4, c:d = 2:3
1:2 
3:4 
( a = 1 × 3 = 3, b = 2 × 3 = 6 and c = 2 × 4 = 8)
(a = a × b, b= b × b and c= b × c) 
a:b:c = 3:6:8 
a:b:c = 3:6:8 and c:d = 2:3
(Note: First a,b,c multiplication with c means 2 and last c means 8
multiplication with d means 3
a:b:c:d = 6:12:16:24 

Basic Computer Knowledge Test Questions and Answers

7.

If a:b=2:3, b:c=4:5 and c:d=4:2 find a:b:c:d? 

   A.) 32:48:8:24
   B.) 8:12:60:24
   C.) 32:18:24:30
   D.) 32:48:60:30

Answer: Option 'D'

a:b = 2:3, b:c = 4:5, c:d = 4:2
2:3 
4:5 
( a = 2× 4 = 8, b = 37 × 4 = 12 and c = 3 × 5 = 15)
(a = a × b, b = b × b and c = b × c)
a:b:c = 8:12:15 
a:b:c = 8:12:15 and c:d = 4:2
(Note: First a=8,b=12,c=15 multiplication with c means 4 and last c = 15
multiplication with d means 2
a:b:c:d = 32:48:60:30 

Basic Computer Knowledge Test Questions and Answers

8.

If  2a=6b and 9b=7c, Find a:b:c? 

   A.) 42:18:14
   B.) 3:9:7
   C.) 9:27:22
   D.) 21:7:9

Answer: Option 'D'

(2a = 6b => a/b = 6/2)
and (9b = 7c => b/c = 7/9) 
=> a:b = 6:2 and b:c = 7:9 
a:b:c = 42:14:18 = 21:7:9

Basic Computer Knowledge Test Questions and Answers

9.

If 0.4:1.4 :: 1:4:x, then x=?

   A.) 49
   B.) 4.9
   C.) 0.49
   D.) 0.4

Answer: Option 'B'

0.4 × x = 1.4 × 1.4 
x = 1.4 × 1.4/0.4 = 14/10 × 14/10 × 1/(4/10) 
14/10 × 14/10 × 10/4 
7/10 × 7 = 49/10 = 4.9

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10.

If x:y=5:3 then (8x-5y) : (8x+5y)=? 

   A.) 5:13
   B.) 13:5
   C.) 5:11
   D.) 11:5

Answer: Option 'C'

x/y = 5/3 (Given) 
(8x − 5y)/(8x + 5y) 
8(x/y) − 5/8(x/y)+5 
( on dividing Nr and Dr by y) 
(8(5/3) − 5)/(8(5/3) + 5) 
(40/3 − 5/1)/(40/3 + 5/1) 
[(40 − 15)/3]/[(40 + 15)/3] 
25/55 = 5/11 
(8x-5y):(8x+5y) = 5:11 

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