This video is a quick reminder of LCM – Lowest Common Multiple – word problems for GCSE maths, and is aimed at around grade 5.
– stop the video
– work through the questions
– compare your solutions
I hope the video helps and please do leave a comment – thanks!
Download a copy of the questions here:
Here's a copy of the written answers:
1. Bus A and Bus B both leave Leeds at 11.00am. Bus A stops every 8 minutes and Bus B stops every 14 minutes. Assuming that both buses are on a circular route, when could they both meet in Leeds again?
2. My first snooze alarm goes off every 6 minutes
My second snooze alarm goes off every 7 minutes
My third snooze alarm goes off every 8 minutes.
Assuming all the alarms went off at 7.00am, how long will it be before they all sound again …. and I absolutely, have to, get up?
3. A lighthouse has two lights. One that flashes every 14 seconds, and one that flashes every 2 minutes. If the lights flash together at 10.00pm, when will they next flash together?
4. A car service manual recommends changing the oil filter every 3000 miles, the air filter every 5000 miles, and the fuel filter every 8000 miles.
The car is driven 1500 miles per month.
If all three were changed on 1st January, after how many months should they all be changed again?
- Always use a factor tree to find the prime factors
- Divide by 2, then 3, then 5 to make your working easier to follow
- If you have time, check your prime factors multiply to the original number
- A venn diagram can be a useful way of showing your results
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