Question

Check whether the following are in proportion? or not? 

(a) 10, 12, 15, 18 

(b) 11, 16, 16, 21 

Answer 1

a) 10, 12, 15, 18 

Given numbers are 10, 12, 15, 18. 

If a, b, c, d are in proportion i.e., a : b :: c : d, 

then product of extremes = product of means (a.d = b.c)

a : b :: c : d 

10 × 18 = 12 × 15 

180 = 180 

If the product of extremes is equal to the product of means, then the given numbers are in proportion. 

So, 10, 12, 15 and 18 are in proportion,

b) 11, 16, 16, 21 

Given numbers are 11, 16, 16, 21. 

If a, b, c, d are in proportion i.e., a : b :: c : d,

 then product of extremes = product of means (a.d = b.c)

11 × 21 = 16 × 16

231 ≠ 256 

Here the product of extremes is not equal to the product of means, then the given numbers are not in proportion. 

So, 11,16, 16 and 21 are not in proportion.