Step 9: Estimate Answers Year 4 Addition and Subtraction Learning Video Clip
Sebastian the explorer has climbed into the canopy of the jungle. He needs to use his knowledge of estimating answers quickly whilst wandering on the tree branches.
More resources for Autumn Block 2 Step 9.
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Discussion points for teachers
- Which different routes can Sebastian take by rounding the distances to the nearest 100? Discuss the different combinations that can be made to create the answer. Discuss which digit to look at when rounding to the nearest 100. This question is open-ended for the children to explore.
Various answers, for example: 1,300m, 1,800m and 2,300m.
- Round the amounts to the nearest 10 to see if he can collect any more. Discuss which digit to look at when rounding to the nearest 10. Discuss what other steps are needed in question, discuss which operation to choose is the most efficient.
1,239ml = 1,240ml; 1,611ml = 1,610ml; 1,795ml = 1,800ml. This gives a rounded total of 4,650ml, so he can collect more.
- Which two vines are the best estimate for Sebastian to climb down? Discuss what each number could be rounded to. Discuss which will give the closest answer to the original numbers.
22 hundreds and 20 tens + 1 thousand, 21 hundreds and 33 tens.
- Place the numbers back in the calculations so that, when rounded to the nearest 1,000, they give the correct answer. Discuss which digit to look at when rounding to the nearest 1,000. Discuss if there is more than one answer for each question.
Various answers, for example:
5,099 – 1,979 rounds to three thousand; 1,803 + 3,449 rounds to five thousand; 3,367 + 5,501 rounds to nine thousand; 8,763 – 6,549 rounds to two thousand
National Curriculum Objectives
Mathematics Year 4: (4C2) Add and subtract numbers with up to 4 digits using the formal written methods of columnar addition and subtraction where appropriate
Mathematics Year 4: (4C3) Estimate and use inverse operations to check answers to a calculation
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