Lesson 102: Real-world: Exact or Approximate
Sometimes an exact answer is needed when an approximate answer is not close enough
This is not just in math class, but in the real world.
SORT CARDSWhich situations will require an actual amount or an estimate?
Exact Approximate
Cups in a recipe Gallons in a lake
Exact amount of gas a car holds Amount of cake needed for a birthday party
Kilometers to finish a race ‘Sporks’ the cafeteria orders to make sure there is enough
Yards on a football field The number of blow fish in the ocean
Minutes in each music class Amount of spaghetti to boil for a family of four
People who voted in an election Milk consumed by the average 5th grader in one year (at home & school)
Square feet of carpet for a bedroom
The amount of food the cafeteria prepares each day for the whole school district
Actual ounces in a milk jug How much money is needed to buy groceries
Sometimes we will need to know which is the
BEST way to estimate
A. Round each amount to the nearest $100,
then subtract to find the difference
B. Round each amount to the nearest $10,
then subtract to find the difference
C. Subtract the amounts, then round the difference to the nearest $10
D. Subtract the amounts, then round the difference to the nearest $1
A. Adding $10.00 a total of nine times
B. Thinking $9.00 x 9 and $1.00 x 9 and
then adding them together
C. Multiplying twelve by $9.00
D. Multiplying nine by $10.00
Carrie ESTIMATED the sum in the problem by rounding each number to the nearest thousand before adding. Which should
have been Carrie’s ESTIMATE?
The answer would be….B. 51,000
How could Carrie get the incorrect answers?
46,00056,00052,000
Bobby wants to ESTIMATE the sum of problem by rounding each fraction to the nearest
whole number before adding. Which should be his
ESTIMATE?
The answer would be: C. 27
Talk with a shoulder partner about HOW you would solve this problem.
A. Add the amounts, round to the nearest $100, and then multiply by 5
B. Round each amount to the nearest $100, add, and then multiply by 5
C. Add the amounts and then round to the nearest $100
D. Round each amount to the nearest $100 and then add
With a shoulder partner, think of some words in a problem that tell you they want an EXACT answer
How manyTotal costExactly or exactHow muchActual
A. 35,058B. 34,058C. 40,000D. 35,057
B. 34,058
Time out: THINK – how would you solve it?PAIR – with neighborBe ready to SHARE!
A. 195 ½ inchesB. 200 inchesC. 195.9 inchesD. 196
C. 195. 9
A. $16.31B. $33.69C. $44.69
D. $33.68
B. $33.69
What mistake was made to get:
A.$16.31C.$44.69D.$33.68
Independent practice page
Journal: Write how you would estimate the sum of 7,345 and 3,942. What method would you use?
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