Trick of the trade:
Divide both 40 and 55 by the largest possible common exact divisor number, i.e. 5 in this case
This gives 8 and 11 correspondingly. Then multiply 8 with 11 = 88 and then multiply
88 with the 5=440
In the case of prime numbers the first step does not apply, just multiply the two numbers to gether and get the answer.
All the best,
What method or formulae can I use to solve the maths below ?
Two trains are running, on separate tracks, round a model railway layout. One completes a circuit every 40 seconds and the other every 55 seconds. The trains start together at the station. How long, in minutes and seconds, will it be before they are at the station together again ?
The answer given is 7 mins 20 secs