Step-by-step explanation:
anything whole or complete is designated as 100%.
what is x% of that whole ?
well, we need to multiply the whole with the same factor we need to multiply 100 with to get x.
100×f = x
f = x/100
whole × f = x% of the whole
so, when we are looking for 5%, what did that mean ?
it means that x = 5, and f = 5/100.
therefore, 5% of $13 is
13 × 5/100 = 65/100 = 0.65
so,
basic cost = $13
tax rate = 5%
tax amount = $0.65
and
basic cost = $13
tax amount = $0.65
total cost = 13 + 0.65 = $13.65
as 5/100 = 0.05
we have seen that the tax amount is simply $13×0.05
and when we add the tax amount to the basic cost, we need to add $13×1 (basic cost) to the $13×0.05 (tax amount), and we get as total
total cost = $13×(1+0.05) = $13×1.05 = $13.65
so, the decimal factor we can use directly without going through all the detail above is : 1.05
