Using mental math, the approximate tip to leave for a bill of $81.79, if you tip 15% would be a. $8.20 b. $10.30 c. $12.30 d. $16.40

The easiest way to count 15% from $81.79 is:

1. Since $81.79 is 100%, then if you want to find 10% from this number, you should simply divide by 10. Then 10% from $81.79 is $8.179.

2. Now you know that 10% is $8.179, then 5% is a half of this sum, i.e. $8.179:2=$4.0895

3. 15%=10%+5% and in $ it is $8.179+$4.0895=$12.2685 that is nearly $12.30.

correct choice is C.

for ex: the reciprocal of 3/4 is 4/3. it is the opposite.

reciprocal definition:

a mathematical expression or function so related to another that their product is one; the quantity obtained by dividing the number one by a given quantity.

50.6

step-by-step explanation: