Time, Measurement & Unit Conversion — 11+ Topic Guide

Part of the GrammarMock topic guides.

Why this topic is quietly dangerous

Time and measurement questions look like primary-school material, so families skip practising them — then the child meets "a film starts at 19:25 and runs for 1 hour 47 minutes" under exam pressure and burns ninety seconds on it. Time arithmetic is NOT ordinary arithmetic (60s and 24s instead of tens), and that mismatch is exactly what the examiners exploit.

The conversion table to know cold

The skill being tested is decimal handling: 3.27 m = 3,270 mm requires ×1,000 done confidently on a decimal. Practise with awkward decimals (2.45 m, 0.8 kg, 1.05 litres), not round numbers.

Direction check: converting to a SMALLER unit means MORE of them (multiply); to a BIGGER unit means fewer (divide). "4,500 ml in litres" → bigger unit → divide → 4.5 L. Children who memorise "×1,000" without the direction rule divide when they should multiply.

Time arithmetic — the bridging method

"A train leaves at 14:35 and the journey takes 3 hours 48 minutes. When does it arrive?"

Never add minutes like ordinary numbers. Bridge in stages:

1. Add the whole hours: 14:35 + 3 h = 17:35
2. Add minutes to the next hour: 17:35 + 25 min = 18:00 (used 25 of the 48)
3. Add what's left: 48 − 25 = 23 min → 18:23

The staged method is slower to describe and faster to do correctly. The all-at-once method produces 17:83 → "18:23" only if the child converts correctly under pressure — many don't.

Backwards versions ("a film ends at 21:12 after 1 h 47 min — when did it start?") use the same bridging in reverse.

24-hour clock: afternoon times need +12 (4:40 pm = 16:40). The exam mixes formats within one question deliberately.

Timetable questions

Reading a bus/train timetable column correctly is the whole skill: find the departure AFTER a given time ("Jai arrives at the stop at 09:50 — the 09:47 has gone; the next is 10:04"), then compute the journey length by bridging. Trap: the tempting-but-departed earlier service.

Duration across days

"How many days from 15th March to 24th April?" — count the rest of March first (31 − 15 = 16 days), then add April days. Month lengths matter: 30 days hath September, April, June and November. Day-of-week cycling uses remainders: 100 days after Wednesday → 100 ÷ 7 = 14 r 2 → two days on → Friday.

Speed, distance, time

The 11+ tests the triangle gently but definitely:

• Speed = distance ÷ time (252 km in 3 hours → 84 km/h)
• Distance = speed × time (72 km/h for 45 min → 45 min is ¾ h → 54 km)
• Time = distance ÷ speed (540 km at 60 km/h → 9 hours)

Fractional hours are the trap: 45 minutes is 0.75 hours, not 0.45. Two hours twenty minutes is 2⅓ hours. Convert time to hours-as-fractions BEFORE touching the formula.

The stretch version: average speed over a two-part journey = TOTAL distance ÷ TOTAL time — never the average of the two speeds. (90 km at 45 km/h then 90 km at 90 km/h: 180 km in 3 h = 60 km/h, not 67.5.)

Reading scales and clocks

Analogue clock reading still appears. The minute hand does the minutes (each number = 5 minutes); the hour hand between numbers belongs to the EARLIER hour. For clock-angle questions, see the Angles & Geometry guide.

One-week plan

• Day 1: the conversion table with awkward decimals
• Day 2: time bridging forwards, 6 questions
• Day 3: bridging backwards + 24-hour mixes
• Day 4: timetables
• Day 5: speed-distance-time with fractional hours
• Day 6: durations across days + day-of-week remainders
• Day 7: mixed 15-question drill from the mini-tests