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Unit conversion
I worked these out from the practice questions. Each code says where to start reading, where to stop, what you can skip, and why it is safe.
1. Big to small check
- Start:
- Decide if you go from a big unit to a small unit.
- Stop:
- Stop when you know if the number should grow or shrink.
- Skip:
- Skip trying to remember whether to multiply or divide.
- Why:
- Questions 1, 2 and 3 are all fixed by this check; option 381.0 in Question 3 grows when it should shrink.
Used in questions 1, 2, 3
2. Last unit first
- Start:
- Start at the last sentence and underline the unit that is wanted.
- Stop:
- Stop and write that unit at the end of your work.
- Skip:
- Skip the other numbers until you know the path.
- Why:
- Questions 6, 7 and 8 all have a middle unit (liters, minutes) as a wrong option.
Used in questions 6, 7, 8
3. Convert both parts of a rate
- Start:
- Split the rate into top unit and bottom unit.
- Stop:
- Stop after both are changed.
- Skip:
- Skip half conversions.
- Why:
- Question 4 gives 1.5 if only the hours are changed.
Used in questions 4, 8
4. Convert the sides before the area
- Start:
- Change each length to the new unit.
- Stop:
- Stop and then multiply the new lengths.
- Skip:
- Skip trying to remember the square factor.
- Why:
- Question 5 gives 200,000 only after 400 × 500.
Used in question 5
5. Use the answer's size
- Start:
- Compare options to the starting number.
- Stop:
- Stop when only one size is sensible.
- Skip:
- Skip options that are far too big or small.
- Why:
- In Question 2, 25 is far too small and 250 is far too large for 2.5 hours in minutes.
Used in questions 2, 3, 7
6. Calculator chain
- Start:
- Type the whole chain, such as 0.5*24*60*60/1000.
- Stop:
- Stop after the result appears.
- Skip:
- Skip writing every middle number.
- Why:
- Questions 6 and 7 are long chains and one typed line has fewer slips.
Used in questions 6, 7
7. Speed shortcut
- Start:
- Remember km/h divided by 3.6 is m/s.
- Stop:
- Stop when you get the answer for Question 4 as 90 ÷ 3.6.
- Skip:
- Skip the long conversion if you remember it.
- Why:
- This shortcut matches the long chain in Questions 4 and 8.
Used in questions 4, 8
8. Conversion facts table: link the chain
- Start:
- Read the facts table and write the chain from the starting unit to the asked unit (GB to MB to bits).
- Stop:
- Stop when each arrow has one fact from the table.
- Skip:
- Skip facts that are not in your chain; extra facts are decoys.
- Why:
- Question 13 needs 1 GB = 1,000 MB and 1 byte = 8 bits, but Question 14 needs only the hectare fact.
Used in questions 9, 13, 14
9. Clock time is not a decimal
- Start:
- Change minutes to hours by dividing by 60; never write 3 h 20 min as 3.2.
- Stop:
- Stop when the time is a fraction like 3 1/3 or a decimal you divided yourself.
- Skip:
- Skip reading 135 minutes as 1 hour 35.
- Why:
- Question 10 (135 ÷ 60 = 2.25) and Question 15 (3 h 20 = 3 1/3 h) both have a wrong option made from the clock digits.
Used in questions 10, 15
10. Volume and rates: find the unit per 1
- Start:
- Turn each fact into a per-one unit rate (25 mg per mL, 1,000 cm³ per liter).
- Stop:
- Stop when your last division gives the unit the question asks for.
- Skip:
- Skip doing the whole chain in one step if the numbers are not simple.
- Why:
- Questions 12 and 16 end with a division into the unit asked (liters, mL), and the wrong options are the middle units.
Used in questions 11, 12, 16