Finding a number

Example 1

$48$ is $25%$ of what number?

Guide to show how to find a number example 1

Multiply both sides by $48$ to get $x$ on its own (what ever you do to one side you do to the other).

$(4\ \ cancel100times48)/cancel25=(xtimescancel48)/cancel48$

$4times48=x$

$x=4times48$

$x=192$

Answer: $48$ is $25%$ of $192$

Example 2

What is $35%$ of $26$ ?

Guide to show how to find a number example 2

Multiply both sides by $x$ to get $x$ on its own (what ever you do to one side you do to the other).

$(xtimes100)/35=(26timescancelx)/cancelx$

$(100x)/35=26$

Multiply both sides by $35$ to get $x$ on its own.

$(100xtimescancel35)/cancel35=26times35$

$100x=26times35$

Divide both sides by $100$ to get $x$ on its own

$(cancel100x)/cancel100=(26times35)/100$

$x=(26times35)/100$

$x=9.1$

Answer: $9.1$ is $35%$ of $26$

Example 3

I’m going to buy $£33.50$ , excluding tax, worth of food. The sales tax is $19%$ . How much tax do I pay and how much will the total bill be?

This is the same as saying:

What is $19%$ of $£33.50$ ?

Guide to show how to find a number example 3

Multiply both sides by $x$ to get $x$ on its own (remember what ever you do to one side you do to the other).

$(100timesx)/19=(33.50timescancelx)/cancelx$

$(100timesx)/19=33.50$

Multiply both sides by $19$ to get $x$ on its own

$(100xtimescancel19)/cancel19=33.50times19$

$100x=33.50times19$

Divide both sides by 100 to get X on its own

$(cancel100x)/cancel100=(33.50times19)/100$

$x=(33.50times19)/100$

$x=6.37$

Answer: The tax is $£6.37$ and the total price will therefore be $£6.37 + £33.50 = £39.87$

Example 4

A coat costs $£88.00$ and is then discounted in a sale by $20%$ . How much will the sale price be?

Guide to show how to find a number example 4

NOTE:

With a discount of $20%$ the new price is $80%$ of the original.

Guide to show how to find a number example 4 pt2

Multiply both sides by $x$ to get $x$ on its own (what you do to one side you do to the other).

$(100timesx)/80=(88.00timescancelx)/cancelx$

$(100x)/80=88.00$

Multiply both sides by $80$ to get $x$ on its own.

$(100xtimescancel80)/cancel80=88.00times80$

$100x=88.00times80$

Divide both sides by $100$ to get $x$ on its own.

$(cancel100x)/cancel100=(88.00times80)/100$

$x=(88.00times80)/100$

$x=70.40$

Answer: The sale price will be $£70.40$