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Given that 43 × 16 = 688, find the answer to:
1) 688 ÷ 16
2) 1.6 × 4300
3) Estimate 68.8 ÷ 4.3
4) 68.8 ÷ 4.3
1) 688 ÷ 16 = 43
2) 1.6 × 4300 = 6880 (16 was divided by 10, 4300 was multiplied by 100, overall change was x10 to give 6880)
3) 70 ÷ 5 = 14 (use the simplest numbers possible - 70/4 is harder)
4) 68.8 ÷ 4.3 = 16 (both sides were divided by 10 so the answer doesn’t change from the original sum)
What is estimation?
A rough calculation used to make answering problems easier
Estimate 7.1×97
7×100=700
Isla uses her mobile phone while abroad. She received 3 minutes of calls at 88p per minute. She made 7 minutes of calls at 71p per minute. She sent 4 text messages at 52p per message. Estimate the total cost.
3×90=270, 7×70=490, 4×50=200
270+490+200=960p or £9.60
702.1 + 299.3/1.9 × 5.1
700+300=1000, 2×5=10
1000/10=100
(4.022 +√102)/0.51
4+10=14, 14×2=28
√(50.77/0.513)
50×2=100
√100=10
Note 
Flashcard (102)