Dividing Decimals
You can use long division to divide a decimal by a whole number. Divide as with whole numbers. Then line up the decimal points in the quotient and the dividend.
Example 1:
Ticket prices: The cost of 11 tickets to see Taylor Swift was $574.75. How much did each ticket cost?
To find the cost of each ticket, divide 574.75 by 11.
52.25 Divide as you would with whole numbers.
11 )574.75 Line up decimal point in quotient with decimal point in dividend.
-55 ↓
24
- 22 ↓
27
-22 ↓
55
- 55
0 Stop dividing when you get a zero remainder.
Answer: Each ticket cost $52.25
To check for reasonableness of a quotient, use compatible numbers.
Compatible numbers are numbers that make a calculation easier.
11 - - - - - > 10 Round divisor to place of leading digit.
574.75 - - - - > 570 Round dividend to nearest multiple of 10.
Because 570 / 10 = 57, the quotient in Example 1 is reasonable.
DIVIDING BY A DECIMAL:
When you divide by a decimal, multiply both the divisor and the dividend by a power of ten that will make the divisor a whole number.
multiply by 10
19.6 ÷ 4.78 =======> 196 ÷ 47.8
Examples:
Divide
a. 4.908 / 4.09
Guided Practice:
1. Susan already has 10,352 songs on her iPod. She gets four iTunes gift cards for her birthday, they are worth $25.00 $15.00 $20.00 and $10.00 If she buys each song for $.0.75; how many songs will she have all together on her iPod after spending all her gift cards?
2. In baseball, a batting average is calculated to determine how successful a player is as a batter. To calculate: take the number of hits divided by the number of times at bat. Find the batting average of a player who hit the ball 6 times out of 29 times up at bat. Round the number to the nearest thousandth.
3. There is a buy two get one free sale on video games at the store. If you buy 2 video games that are each 46.99 and get a third game free, what is the mean cost of each video game?
4. Find the cost per pound of a watermelon. The watermelon costs $6.50 and weighs 7.9 pounds. Round to the nearest tenth.