Estimation with Fractions
name that term: a whole number or fraction that is easy to use when you estimate
BENCHMARK
5/12 + 1/4
8/12 or 2/3
4/5 - 1/4
11/20
11/12 - 4/6
3/12 or 1/4 (simplest form!)
Use benchmarks to estimate: 11/18 - 2/9
1/2 - 0 = 1/2
2/5 + 1/2
9/10
13/16 - 1/4
9/16
1/7 + 1/2
9/14
name that term: fractions with the same denominator (4/12 & 3/12 for example)
common denominators
Alex rode his scooter from his house to the park, 1/3 mile. Later, he road 1/8 mile from the park to baseball practice. How far did Alex ride in total?
1/3 + 1/8 = 8/24 + 3/24 = 11/24
2/9 - 1/6
1/18
7/8 - 2/3
5/24
How would you estimate which benchmark 27/50 is closer to 1/2 or 1?
25/50 = 1/2 and 50/50 = 1. since 27 is closer to 25 than it is to 50, 27/50 is closer to 1/2 than it is to 1.
1/4 of the candy on our gingerbread house are chocolate wafers. 3/8 of the candy are candy canes. What fraction of the gingerbread house is covered in chocolate wafers or candy canes?
1/4 + 3/8 = 5/8 of the house
Why do fractions need o have a common denominator before you add or subtract them?
the denominator tells you what size parts you are adding or subtracting. The parts must be the same size when you add or subtract.
Carl has 3 lengths of cable: 5/6 yd, 1/4 yd, and 2/3 yd long. If he uses 1 yard of cable, how much cable is left?
5/6 + 1/4 + 2/3 = 10/12 + 3/12 + 8/12 = 21/12 or 1 9/12 yd or 1 3/4yd (simplest form!). if you subtract 1 yard, you are left with 3/4 yd cable.
Steve is making breakfast. The recipes call for 7/8 cup of milk for grits and 3/4 cup for biscuits. He only has 2 cups of milk. Does he have enough to make his breakfast? Explain.
If he has enough milk, about how much milk will he have left? If he does't have enough milk, about how much will he need?
yes! both recipes call for less than 1 cup, so the 2 recipes will use less than 2 cups together.
7/8 is about 1, so the recipes will use about 1 3/4 cups. And 2 cups - 1 3/4 cups = 1/4 cup
How can we consider fractions equivalent if they are made up of different numbers? (provide an example of equivalent fractions)
2/3 = 4/6 = 6/9 = 8/12...equivalent fractions have the same value or express the same amount of a whole. You can use a common multiplier to move between equivalent fractions.
Textbook, page 284, # 17
9/16 inch; 13/16 - 1/4 = 9/16
Jereen spent 1/4 hr on homework before school, another 1/2 hr after she got home from school, and a final 1/3 hr after dinner. Did she spend more or less than 1 hour on homework in all? Explain.
Jereen spent more than 1 hour on homework: You could use a common denominator to make equivalent fractions: 3/12 + 6/12 + 4/12 = 13/12.
You could also reason that 1/4 + 1/2 would = 3/4...1/3 is greater than 1/4, so you know it would be longer than 1 hour.