10.5% of what number is 420?

Question

2453 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2017-05-09T05:15:59

Number is 4000.

Let the number be $x$ .

$therefore$ $x(105/1000) = 420$
$rArr$ $x = (cancel420 * 1000)/cancel105 = (4 * 1000) = 4000$

Answer 2 · 2017-05-09T05:36:06

$10.5%$ of 4000 is $420$

We know that $10.5%$ of the number we will call $N$ is $420$ .
We know that $100$ of the number is $N$ .

So now we can equate the two lines above by following what we have written:

$10.5/100 = 420/N$

Then cross multiply:

$10.5N = 100*420$

$cancel(10.5)N = 100*cancel(420)4$

$N = 4000$

To check this answer we can calculate $10% or 1/10 of 4000 = 400$

which is reasonably close to the $10.5%$ being $420$ as given above.