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 CARDS Which situations will require an actual amount or an estimate?
ExactApproximate Cups in a recipeGallons in a lake Exact amount of gas a car holdsAmount 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 fieldThe number of blow fish in the ocean Minutes in each music classAmount of spaghetti to boil for a family of four People who voted in an electionMilk consumed by the average 5 th 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 jugHow much money is needed to buy groceries
Sometimes we will need to know which is the BEST way to estimate
Which is the best way to ESTIMATE the difference between $95.43 and $41.26? 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
AA. Adding $10.00 a total of nine times BB. Thinking $9.00 x 9 and $1.00 x 9 and then adding them together CC. Multiplying twelve by $9.00 DD. 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 A. 46,000 B. 51,000 C. 56,000 D. 52,000
How could Carrie get the incorrect answers? 46,000 56,000 52,000
An addition problem is shown below: 1 5/ / / /5 Bobby wants to ESTIMATE the sum of problem by rounding each fraction to the nearest whole number before adding. Which should be his ESTIMATE?
A. 25 B. 28 C. 27 D. 30 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 many Total cost Exactly or exact How much Actual
A. 35,058 B. 34,058 C. 40,000 D. 35,057
B. 34,058
Time out: THINK – how would you solve it? PAIR – with neighbor Be ready to SHARE!
A. 195 ½ inches B. 200 inches C inches D. 196
C
A. $16.31 B. $33.69 C. $44.69 D. $33.68
B. $33.69
What mistake was made to get: A. $16.31 C. $44.69 D. $33.68
Independent practice page Journal: Write how you would estimate the sum of 7,345 and 3,942. What method would you use?