Rounding Rules for Rounding 1 IDENTIFY THE PLACE

Rounding

Rules for Rounding 1. IDENTIFY THE PLACE THAT YOU ARE ROUNDING TO. 2. LOOK AT THE NUMBER TO ITS RIGHT. § 5 OR MORE, RAISE THE SCORE. • 4 OR LESS, LET IT REST 3. ALL OF THE NUMBERS TO THE RIGHT OF THE PLACE WILL BECOME ZERO. Examples: 1. ) Round 345 to the nearest ten. 345 5 is “ 5 or more”, so raise the score. 350

Rules for Rounding 2. ) ROUND 43. 42 TO THE NEAREST TENTH. 43. 42 2 is “ 4 or less”, so let it rest. 43. 4 3. ) ROUND 8. 75 TO THE ONES PLACE. 8. 75 7 is “ 5 or more”, so raise the score. 9

Try These in your Notebook Directions: Use the number below to round to the given place values 45, 678, 934. 5678 1. T E N T H S - _45, 678, 934. 6 ________ 2. T E N T H O U S A N D - _ _ 45, 680, 000 _________ 3. T H O U S A N D T H - _ _45, 678, 934. 568 __________ 4. T E N M I L L I O N - _ 50, 000 __________ 5. N E A R S T W H O L E N U M B E R S - _ _45, 678, 935 _____

Estimation

Estimation ed i f pli l m Si nta tion Estimation is: me cula using easy mental strategies l ca Q nu uick en mbe ly a an oug r t nd e sw h t ha a er o t is sily to the cl ge be ex ose t a us ac ef t ul using number sense using a variety of strategies getting close to the exact answer It is not: just a guess doing hand calculations using a calculator exact

Try These Directions: Get a quick estimate in your head. Do the problem. Check to see if your answer is reasonable. 1) 456 + 3497 + 599 = Good estimate would be 5, 100 Another good estimate 4, 600 Actual Answer: 4, 552 2) 578 + 2054 + 3965 = Actual Answer: 6, 597 Good estimate would be 6, 600 Another good estimate 7, 000

Real World Problems

Can I buy four for $100? E n i a l xp 23 Yes a) 4 x $25 = $100 and $23 is less than $25 b) $23 rounds to $25 and 4 x $25 = $100 (high estimate) c) $23 rounds to $20 and 4 x $20 = $80 (low estimate)

Ca n. I bu yt hre ef or $1 Explain No 3 x 3 x $40 $3 is $ 3 is 12 $9 0 9 $3 7 00 ?

Can I buy five for $60? n i a l xp E No a) 5 x $15 = $75 which is more than $60. b) 5 x $14 = $70 which is more than $60. c) $60 divided by 5 = $12, and $13. 87 is more than $12. 00. The soccer ball would have to cost ______ $12. 00 or less for me to purchase five of them for $60.

Can I buy three for $20? Ex pla $4 . 95 Yes a) 3 x $5 = $15 in

Estimating with Compatible Numbers (When numbers are grouped together to make computations easier; estimation becomes almost entirely “mental”. ) Often used to estimate the answer to multiplication and division problems. Compatible numbers make it much easier to estimate the answer to a problem.

142 ÷ 59 Can you think of a pair of numbers, that are close to these, that can be divided mentally? Ac 140 ÷ 70 =2 120 ÷ 60 =2 t Ans ual wer 2. 4 :

226 ÷ 71 Can you think of a pair of numbers, that are close to these, that can be divided mentally? Ac 240 ÷ 80 =3 210 ÷ 70 =3 240 ÷ 60 =4 t Ans ual wer 3. 2 :

54 x 7 Can you think of a pair of numbers, that are close to these, that can be multiplied mentally? Ac 55 x 10 =550 50 x 10 =500 60 x 5 = 300 t Ans ual wer 378 :

267 x 13 Act Ans ual wer 3, 4 : 71 Can you think of a pair of numbers, that are close to these, that can be multiplied mentally? 270 x 10 = 2, 700 300 x 10 = 3, 000 250 x 10 = 2, 500

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