1. Round 907 to 2 significant figures (s.f.): - The first two digits are 9 and 0. - Look at the third digit (7), which is greater than 5, so round up. - Result: $910$ 2. Round 8.934 to 1 s.f.: - First digit is 8. - Next digit is 9, which is greater than 5, so round up. - Result: $9$ 3. Round 100.5 to 3 s.f.: - Digits: 1, 0, 0. - Next digit is 5, so round up the last significant figure. - Result: $101$ 4. Count significant figures in 0.00340: - Leading zeros are not significant. - Digits 3, 4, and trailing zero count. - Total s.f.: $3$ 5. Count significant figures in 50120: - Trailing zero without decimal is ambiguous, usually not significant. - Digits 5, 0, 1, 2 count. - Total s.f.: $4$ 6. Round 134.5 to nearest whole number: - Decimal part is .5, round up. - Result: $135$ 7. Round 3.14159 to 4 s.f.: - First 4 digits: 3, 1, 4, 1. - Next digit is 5, round last digit up. - Result: $3.142$ 8. Round 25900 to 2 s.f.: - First two digits: 2, 5. - Next digit is 9, round up. - Result: $26000$ Standard Form: 9. Write 502000 in standard form: - Move decimal 5 places left: $5.02 \times 10^{5}$ 10. Write 0.00093 in standard form: - Move decimal 4 places right: $9.3 \times 10^{-4}$ 11. Convert $3.2 \times 10^{5}$ to ordinary number: - $3.2 \times 100000 = 320000$ 12. Convert $7.01 \times 10^{-3}$ to ordinary number: - Move decimal 3 places left: $0.00701$ 13. Write 84000 in standard form: - Move decimal 4 places left: $8.4 \times 10^{4}$ 14. Write 0.056 in standard form: - Move decimal 2 places right: $5.6 \times 10^{-2}$ 15. Convert $1.5 \times 10^{2}$ to ordinary number: - $1.5 \times 100 = 150$ 16. Convert $4.8 \times 10^{-4}$ to ordinary number: - Move decimal 4 places left: $0.00048$ This method involves identifying significant digits, rounding based on the next digit, and converting numbers to/from standard form by moving the decimal point accordingly.