Is the solution given by K.B correct then?
Actually if you closely analyse the problem, you will find that you need prime numbers like 13, 59, 67, 83 etc. to solve the number and the sum total of digits of the answer will always be "9" (for eg. 7.47 = 7 + 4 + 7 etc.) as digit 3 is involved both in addition and multiplication.Fraction is a must because the product of the first number of whole number of 1 x 2 x 3 x 4 itself is beyond their sum, so fractions or decimals are a must to rein in the product going overboard. For eg. 0.5 + 0.5 = 1.0, but 0.5 x 0.5 = 0.25 - notice how drastically the decimal point (or a fraction) can reduce the value.