Question

Kelly's new snowboard is 120% longer than her old snowboard. If the new snowboard is 150 cm, how long is her old snowboard?

Answer 1

12.5 Step-by-step explanation: My friend helped me

Answer 2

The length of Kelly's old snowboard is 125 cm long.

How to find the percentage from the total value?

Suppose the value of which a thing is expressed in percentage is "a'

Suppose the percent that considered thing is of "a" is b%

Then since percent shows per 100 (since cent means 100), thus we will first divide the whole part in 100 parts and then we multiply it with b so that we collect b items per 100 items(that is exactly what b per cent means).

Thus, that thing in number is

$\dfrac{a}{100} \times b$

For this case, let we suppose that:

x = length of Kelly's old snowboard (in cm)

Then, as we know that: new snowboard is 120% longer than her old snowboard, thus:

$\dfrac{x}{100} \times 120 = \text{Length of new snowboard} = 150$

or

$\dfrac{x}{100} \times 120 = 150\\\\\text{Multiplying 100/120 on both the sides}\\\\x \times \dfrac{120}{100} \times \dfrac{100}{120}= 150 \times \dfrac{100}{120}\\\\x \times 1 = x = \dfrac{150 \times 100}{120}\\\\x = \dfrac{15000}{120} = 125 \: \rm cm$

Thus, the length of Kelly's old snowboard is 150 cm long.

Learn more about percent here:

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