The dinner check for a birthday party was $89.50. How do you estimate a 15% tip?

1 Answer
EZ as pi
Nov 1, 2016

#15%# of the bill is about #$13.50#

Explanation:

It is very easy to estimate #10%# of any number - just divide by 10 by moving the decimal point one place to the left.

Once you know #10%# of an amount, it is possible to find #5%# by dividing the value that is #10%# by 2. Adding these answers gives a quick estimate of #15%#

For example: "Find 15% of 300"

#10%# of 300 = 30 and #30 div 2 = 15#

15% of 300 = 30+15 =45

In the same way for this question ...

Treat #89.50# as #$90# Find 10%, then 5%.

#10% +5% = $9+%4.50 = $13.50#

#15%# of the bill is about #$13.50#

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