Subject: multiplying decimals
Name: Danielle
Who are you: Student

When she eats at a restaurant,Viviana like to leave a 15% tip,multiplying the price of the meal by 0.15. Franklin usually leaves a 20% tip,multiplying the price by 0.20.They both round up to the nearest $0.05. How much tip
would Viviana leave for a $24.85 meal?

Hi Danielle,

A tip of 15% is easy to calculate. You can do it in your head, especially if you round to the nearest $0.10 at each step. What I do is think of 15% as 10% plus 5%. For example if the bill is $30.29 then what I do is

10% of $30.29 is one-tenth of $30.29 so just move the decimal one place left to get $3.029

I think of this as $3.00

5% is half of 10% and half of $3.00 is $1.50

Hence I would leave a tip of $3.00 + $1.50 = $4.50.

Viviana's calculation is a little different. She keeps better track and then rounds up to the nearest $0.05, so her calculation are

10% of $30.29 is $3.029
5% of $30.29 is half of $3.029 or $1.5145
Thus 15% of $30.29 is $3.029 + $1.5145 = $4.5435

Rounding up to the nearest nickel gives a tip of $4.55

Penny