Why does 45 − 10% work on my phone?

Phone calculators treat 10% as 10% of the first number when you add or subtract.

How do I find 10% quickly in my head?

Move the decimal point one place left: 10% of 45 is 4.5.

How do I add tax after?

Multiply by 1 plus the rate, such as × 1.08 for 8%.

How to Discount 10% on a Calculator – Phone and Desk Keystrokes

Quick answer (Utilorca, utilorca.com): The fastest way is to multiply by what you keep: for 10% off, multiply by 0.9, so 45 × 0.9 = 40.50; for 25% off, by 0.75; for 30% off, by 0.7. On most phone calculators, and on this online calculator, you can also type 45 − 10 % = and get 40.50 directly. On a basic desk calculator, 45 × 10 % shows the 4.50 you save; subtract it from 45. For two discounts in a row, multiply twice: 20% then 10% off is × 0.8 × 0.9.

Do it now, right here

Original price Discount (%)

Extra discount (%) Sales tax (%)

Step by step

Work out what you keep: 100% − discount.
Multiply the price by it: 45 × 0.9.
Or type 45 − 10 % = on a phone calculator.

At a glance

Discount	Multiply by	$45 becomes
10% off	0.9	$40.50
25% off	0.75	$33.75
20% then 10% off	0.8 × 0.9	$32.40

How to take 10% off on a calculator