# Math Help - maybe simple percentage question! Help!

1. ## maybe simple percentage question! Help!

Hello,

I need help to make 0.85p into 0.31p and have the percentage shown, so that 85p turns into 31p automatically, what would be the best way to achieve this on a calculator?

Everytime I try I just have to guess, like 85 / 2.7(guess) = 31.481481
then I would do 100 - 31 = 69%

Is this the only way, is there a quicker method?

Thank you
Regards
Chris

2. Hello, Chris!

The question is not clear . . .

I need help to make 0.85p into 0.31p and have the percentage shown,
so that 85p turns into 31p automatically.
What would be the best way to achieve this on a calculator?
I'll take a guess . . .

To change 0.85 into 0.31, we will multiply by some percent.

Let $x$ = the percent.

Then we have: . $0.85x \:=\:0.31$

It follows that: . $x \:=\:\frac{0.31}{0.85} \:=\:0.364705882$

Therefore: . $x\:\approx\:36.5\%$

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Check

$36.5\% \times 0.85 \;=\;(0.365)(0.85) \;=\;0.31025$ . . . close enough!