Word Problem on Simple Interest in Banking

Topic : Investments and Simple Interest

Question : Helen Weller invested $15,000 in an account that pays 12% simple interest. How much additional money must be invested in an account that pays 15% simple interest so that the total interest is equal to the interest on the two investments at the rate of 13%?

Solution :

12% of 15000 = 12/100 * 15000
= 1800

Now let the additional money invested be $x.

So 15% of x = 15/100 * x
= 0.15x

Now 13% of (15000+x) = 13/100 * (15000+x)
=0.13 * (15000 + x)
= 1950 +0.13x

So the equation will be,
1800 + 0.15x = 1950 + 0.13x
Subtracting 0.13x on both sides

1800 + 0.02x = 1950
Subtracting 1800 on both sides

0.02x = 150
Divide by 0.02 on both sides

x = 150 / 0.02
x = 7500