Dalila bought her grandma a music album for $12.50 and then ordered three songs for herself. In total (before tax), she spent $16.37. How much did Dalila spend on each song?

We need to choose the nearest possible rounded off numbers for the estimation.

Step-by-step explanation:

Compatible numbers are the pairs of numbers which are easy to add, subtract, multiply, or divide mentally.

Example 1 (Addition)

600 + 300 = 900

The numbers 600 and 300 are compatible for addition, because the sum of 900 can be easily calculated mentally.

613 + 299 = 912

The numbers 613 and 299 are not compatible for addition, since the sum (912) cannot be easily calculated mentally. To estimate 613 + 299, replace 613 and 299 with the compatible numbers 600 and 300. An estimate of 613 + 299 is found by mentally calculating 600 + 300 = 900.

Example 2 (Subtraction)

20.4 − 3.8 = 16.6

The numbers 20.4 and 3.8 are not compatible for subtraction, since the difference (16.6) cannot be easily calculated mentally. To estimate 20.4 − 3.8, replace 20.4 and 3.8 with the compatible numbers 20 and 4. An estimate of 20.4 − 3.8 is found by mentally calculating 20 − 4 = 16.