Decimals - ordering and rounding N1.1 Extension Starter Explain this statement. On my calculator six million plus 0.000 000 1 is six million! How can you use your calculator to work out this calculation exactly? 34 687 543 236 453 + 984 753 875 813 Challenge How can you work out 123 533 765 × 954 654 301 exactly using a calculator? Preamble An activity to make pupils a little more aware of the limitations of the calculator and to recap on some paper and pencil methods. Possible content Place value, non-calculator methods for calculation. Resources Calculators. Solutions/Notes The calculator gives 6 000 000 + 0.000 000 1 = 6 000 000 because the calculator is not able to display enough digits to give the exact answer. One way to work out the addition on a calculator is to divide up the numbers (indicated by vertical lines). 34 687 | 543 236 453 and 984 | 753 875 813 Begin by working out 543 236 453 + 753 875 813 = 1 297 122 266. Add together the digits from the front of the numbers: 34 687 + 984 = 35 671. Remember that you need to add nine zeroes to the end of this. Then you get 35 671 000 000 000 + 1 297 112 266 = 35 672 297 112 266 . In the challenge pupils will need to split each number of the multiplication into two or more parts, perform individual multiplications (remembering to put on the extra zeroes) and then combine the answers using addition. The final answer is 117 932 040 075 973 265.