Question

What number should be added to each of the numbers 12, 22, 42 and 72 so that th resulting numbers may be in proportion ?​

Answer 1

Answer:

Hence we can say if we add 3 to the numbers 12, 22, 42 and 72 the resulting numbers will be in proportion. So, the correct answer is “3”.

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Answer 2

Answer:

3 should be added to each of the numbers 12,22,42,72 so that the resulting numbers 15,25,45,75 are in proportion.

Step-by-step explanation:

Let the no. added to 12, 22 ,42 and 72 is x

So the new no's become,

first no.=  12 + x

Second no. = 22 + x

Third no. = 42 +x

Fourth no. = 72 + x

According to question ,

No's are in proportion,

So, 12+x : 22 + x : : 42 +x : 72 +x

( 12 + x ) / ( 22 +x) = (42 +x ) / ( 72 +x)

By doing cross multiplication,

(12 + x) ( 72 + x) = ( 22 + x) ( 42 +x)

72 (12 +x ) + x (12 + x) = 42 (22 +x) + x (22 +x)

864 + 72x+ 12x+ $x^{2}$ = 924 +42x+22x+$x^{2}$

864 +84x + $x^{2}$- $x^{2}$  = 924 +64x

84x - 64x =924 - 864

20 x = 60

x= 60 /20

x=3

Resulting numbers are 12+3,22+3,42+3,72+3=15,25,45,75