We have for example 2 numbers, a and b, and their product, number c. So, c = a * b If value of a is increased by 30 percent, it means that the new value will be old value plus 30 percent of the value; so new value is: a1 = a + 30% * a If we elaborate this equation, we get: a1 = a + 30/100 * a, i.e.: a1 = 100/100 * a + 30/100 * a, i.e.: a1 = (100+30)/100 * a, i.e.: a1 = 130/100 * a . Same for other number b: It its value is increased by 20 percent, it means that the new value will be old value plus 20 percent of the value: b1 will be the notation for the new value, and b is the old value b1 = b + 20% * b b1 = 120% * b b1 = 120/100 * b ------------------------------------- When wanting to multiply a1 with b1, we get: c1 = a1 * b1 c1 = 130/100 * a * 120/100 * b When reducing fractions, we get: c1 = 13/10 * a * 12/10 * b When multiplying free numbers and move the order of a and b, we get: c1 = (13*12)/(10*10)*a*b c1 = 156/100 * a * b -> a * b is c (c = a * b), so: c1 = 156% * c c1 = (100 + 56)% * c Which means that the value of c is increased by 56%.
