Question

Two numbers are 20% and 50% respectively of third number. What percent of second number is the first number?
(a) 10% (b) 20% (c) 30% (d) 40% ​

Answer 1

Answer:

40%

Step-by-step explanation:

Let the numbers be a, b and c

a = 20*c/100

a = c/5

5a = c

b = 50*c/100

b = c/2

2b = c

5a = 2b

a/b = 2/5 or

a : b = 2 : 5

% = 2x/5x × 100 = 40%

SHORT METHOD

a. c. b.

1. 5.

2. 1

Now fill the vacant portion with preceding or succeeding numbers and multiply.

a. c. b.

1. 5. 5

2 2. 1

---------------------

2. 10. 5

% = 2/5 × 100 = 40%