Question #c7539

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Answer 1 · 2017-10-12T11:50:32

See explanation

$10=40%$
$1=4%$
$1*25=4*25%$
$25=100%$

Answer 2 · 2017-10-12T16:30:29

Some explanation in detail

$40%" of "25=10$

$color(blue)("Preamble")$

The symbol % is a bit like a unit of measurement but one that is worth $1/100$

So, in the same way we would say $6" of "x->6x$
We can say $40" of "%->40%=40xx1/100=40/100$

This compares very well to (picking some value at random) $3cm$

centi $->1/100$

3 centimetres $-> 3xx$ centi of 1 metre $->3xx1/100xx1" metre"$

$= 3/100" metres"$
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$color(blue)("Answering the question")$

$color(brown)("Breaking the question down into its component parts")$

$40%$ of ........................... $40/100xx?$

Let the unknown value be represented by $x$ giving:
$40%$ of ........................... $40/100xx x->40/100 x$

10 is .................................... $10=?$

10 is 40% of........................ $10=40/100x$

Multiply both sides by $color(red)(100/40)$
This changes the $40/100$ on the right into 1 so 'getting rid' if it, on that side.

$color(green)(10color(red)(xx100/40)color(white)("d")=color(white)("d")40/100color(red)(xx100/40)xx x)$

$100/4=x$

$x=25$