What number should be added to each of the numbers 103, 135, 110 and 144 so that the resulting numbers are in proportion?
Let say, x be the number.
So,Â
$$\frac{103+x}{135+x}=\frac{110+x}{144+x}\ $$
or, $$\left(103+x\right)\left(144+x\right)=\left(135+x\right)\left(110+x\right)\ $$
or, $$\left(103x+x^2+144x+14832\right)=\left(135x+x^2+110x+14850\right)\ $$
or, $$\left(247x+14832\right)=\left(245x+14850\right)\ $$
or, $$2x=18\ .$$
or, $$x=9\ .$$
C is correct choice.
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