Question

Q21. The third proportional of 0.8
and 0.1 is:
0.8 और 0.1 का तृत्यानुपातिक
ज्ञात करे।
(a) 0.05
(b) 0.0125
(c) 0.125
(d) 0.005​

Answer 1

Answer:

b) 0.0125

Step-by-step explanation:

To know,

for the proportional sums,

Formula is

a: b :: b : c

where a ,b,c are the 3 different terms in proportion

Hence by given data

a = 0.8

b = 0.1

c = ?

By formula

=> a : b :: b : c

=> a : b = b:c

=> (a/b) = (b/c)

=> a × c = b × b

=> c = b × b ÷ a = 0.1×0.1÷0.8

=> c = 0.0125

Hence the required answer is 0.0125

Answer 2

Answer: 0.0125

Step-by-step explanation:

Let that third number be x.

Given that 0.8 , 0.1 and x are proportional.

i.e. 0.8 : 0.1 : x

 0.8/0.1 = 0.1/x

0.8 × x = 0.1 × 0.1

Multiplying by 100 in both sides

0.8 × x × 100 = 0.1 × 0.1 × 100

80x = 1

x = 1/80

x = 0.0125

Hence option (b) is correct.

Note: If a,b and c are in proportional then

a/b = b/c