Getting the right answer and still losing the mark in 11 plus maths

Try this one, the way it appears on an 11 plus maths paper.

A night shift starts at 21:50 and ends at 02:20. How many minutes long is the shift?

From 21:50 to 22:00 is 10 minutes. From 22:00 to 02:00 is 4 hours, which is 240. From 02:00 to 02:20 is another 20. So 270 minutes.

Now suppose your child writes 4 hours 30 minutes.

They crossed midnight without tripping over it, which is the whole point of the question and the bit most children get wrong. They have the right length of time, written the way anyone would say it out loud.

And they score nothing. Would you mark that right or wrong?

Why the mark goes

The question did not ask how long the shift is. It asked how many minutes it is. Those are two different questions and only one of them was on the paper.

That is not pedantry, it is most of the difficulty. A selective paper cannot make the arithmetic much harder than the curriculum allows, so it makes the reading harder instead: it buries the question inside a sentence, or asks for one part of the answer rather than all of it, or names the unit it wants and waits to see who noticed.

Now change one word

A night shift starts at 21:50 and ends at 02:20. How long is the shift?

4 hours 30 minutes is right. So is 270 minutes. The question left the unit open, so either one answers it.

This is where marking at home goes wrong, because the rule is not "use the smallest unit" and it is not "copy the unit in the question". It is:

Answer in the unit the question names. If it names none, any correct form will do.

The ten seconds that fix it

Before writing anything, read the last line again and say out loud what the answer has to be. Minutes. Grams. A fraction. A 24 hour clock time. Then write that.

It is not a new method and it is not more practice papers. Practice makes this one worse, because your child gets quicker at the maths and no better at reading the instruction. And it is not a time problem either: the same slip turns up in grams and kilograms, pence and pounds, and every "give your answer as a fraction".

You can check for it on a paper your child has already done. Look only at the ones marked wrong and ask whether the amount was right. If it was, you have found something worth more than a term of revision.

On a SillyMaths paper the mark still goes, because in the hall it will. But the report says what actually happened, rather than filing it under time, so you know whether your child needs teaching or needs ten seconds.