Can you solve this math problem for primary students?
A homework question that was intended for an 8-year-old has left parents clueless.
The question, which was shared on parenting website Mumsnet, asks students to solve a riddle that involves working out what time various lighthouses will shine their lights.
The answer is achieved by working out the common multiples between the schedules of the lighthouses.
Can you solve the homework riddle?
The question has been criticised as being “ridiculous” for primary students to answer.
The puzzle reads, “On the coast there are three lighthouses. The first light shines for 3 seconds then it is off for three seconds. The second light shines for 4 seconds then it is off for 4 seconds. The third light shines for 5 seconds then it is off for 5 seconds. All three lights have just come on together.
“When is the first time that all three of the lights will be off together?
“When is the next time that all three lights will come on at exactly the same moment?”
The math question left parents baffled but they eventually arrived at the same answer that the lights would be off together at six seconds, and they would come on together at 120 seconds.
Parents found that the problem was easiest worked out by finding the time they were off and then finding out when they were off at the same time.
The first light house comes on every 6 seconds, the second every 8 and the third every 10, so you have to work out the lowest number that can be divided by all those numbers – which is 120.
The question frustrated many parents by the level of difficulty being given to students in Year 4.
“That is a ridiculous question and I'm only here to learn something,” one wrote.
Did you solve the problem? Let us know in the comments below.