Question

Use mental math to approximate what a 15% tip would be for a bill of $31.99.

a.
$3.20
b.
$4.80
c.
$5.60
d.
$6.40

Answer 1

letter B bc if you do the actual math it comes to be 4.79 so mentally you would give a 4.80 tip

Answer 2

The whole bill is $31.99 that is 100%. You can use mental math to determine exatcly 15% from $31.99:

1. 15%=10%+5%

2. To find 10% from $31.99 you should simply divide $31.99 by ten. Thus, 10% from $31.99 is $3.199.

3. 5% is half of 10%, then 5% from $31.99 is $3.199:2=$1.5995.

4. 15% from $31.99 is $3.199+$1.5995=$4.7985≈$4.80.

Answer: correct choice is B.