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Estimate Products 2

CCSS: 4.NBT.5. Objective: Accurately estimate products and compare estimates to exact products. Estimate Products 2. In 2-digit by 2-digit multiplication, your only option is to round to the greatest place (the tens). 2 nd: Find the exact product. 1 st: Find the estimated product.

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Estimate Products 2

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  1. CCSS: 4.NBT.5 Objective: Accurately estimate products and compare estimates to exact products. Estimate Products 2 In 2-digit by 2-digit multiplication, your only option is to round to the greatest place (the tens). 2nd: Find the exact product. 1st: Find the estimated product. After finding the first partial product (744 in this problem), put a line through any carried digits. 1 2 93 x 68 90 x 70 Leave some space in case you need to carry a digit when adding the partial products. 1 6,300 4 74 1 +           55 8 0 Before multiplying by the tens digit (6 in this problem), put a place holder zero in the ones place of the partial product. 6, 3 2 4 THINK when you find your product. Is it close to the estimate? The 6 is really 60 which equals 6 x 10. (If it isn’t, there is probably a mistake to find.)

  2. Classwork Directions: Round each factor and multiply to estimate. Then in a separate problem, multiply the original factors to find the exact product. 2nd: Find the exact product. 1st: Find the estimated product. 2nd: Find the exact product. 1st: Find the estimated product. 1. 2. 4 26 x 17 30 41 x 24 40 x 20 x 20 1 600 800 2 4 18 16 +         6 0 +         2 0 2 8 4 4 2 9 8 4 If both factors are rounded up, the estimate will be greater than the exact product. If both factors are rounded down, the estimate will be less than the exact product.

  3. The only exception when stacking factors is when there is a repeated digit. Placing that factor on the bottom could save some work.. When stacking factors, almost always put the greater factor on top. 39 x 62 53 x 77 7. 8. 2nd: Find the exact product. 1st: Find the estimated product. 2nd: Find the exact product. 1st: Find the estimated product. 1 2 62 x 39 60 53 x 77 50 x 40 x 80 1 2,400 4,000 8 1 55 37 1 1 6 0 371 0 +          18 +          4 1 8 0 8 1 2, 4, After putting the place holder 0 in the ones place, you multiplied by 7 in the previous step, so just copy the rest of the partial product from the one above.

  4. Word Problems – Answer in a complete sentence with the correct number and proper label. 13. Which two words tell you to use rounding in order to estimate a product? _____________________________________________________________________ _____________________________________________________________________ The words “about” or “approximately” tell you to use rounding to estimate the product. 14. If both factors in a multiplication problem are rounded up, the estimate will be ______________ the exact product. greater than 15. If both factors in a multiplication problem are rounded down, the estimate will be ___________ the exact product. less than

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