ICSE Class X Math 2013 Solved Paper

Question : 4 of 46

Marks: +1, -0

What number must be added to each of the number 6, 15, 20 and 43 to make them proportional?

Solution:

Let the number must be added be

x

, then the new number

=6+x, 15+x, 20+x, 43+

x

∵

These are proportionals.

\;6+x: 15+x:: 20+x: 43+x

\; \;\; (6+x)(43+x)=(15+x)(20+x)

\;\;\text " or "\; 258+6 x+43 x+x^2\;

=300+20 x+15 x+x^2

\;\;\text " or "\;\;49 x-35 x\;

=300-258

\;\;\text " or "\;\;14 x\;=42

\;\;\text " or "\;\;x\;=3 .

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