Seemingly innocuous Maths question.... Can anyone give me the answer?

[Downnotout]

Schofield and Sims mental arithmetic.

A piece of wood is 1/2 metre long. How many cm does another piece measure which is one and a half times as long.

My first instinct was 75cm (50x1.5) but then I thought do you add the 75 to the 50 making 125cm because that would be 1 1/2 times longer?

Twice as long would be 100cm so how could 1 1/2 times be longer than that?
Am confused. Asked her teacher who said 150cm but then changed her mind and said she would have to think about it.

Is this just a badly written question? It's doing my head in.

75, surely?

You were right the first time. One and a half times as long means multiply by 1.5. Just like twice as long means multiply by 2, half as long means multiply by 0.5, two and half times as long means multiply by 2.5.

So yes, 75cm.

Her teacher is worrying me! 150cm is three times as long.

75cm

75cm is right - that's the same amount again, plus a half. So one and a half times as long.

As you say, twice as long would be 100cm, so longer than one and a half times as long - indeed, it's half as long again, ifyswim.

150cm is three times a long.

Teacher will be when she gets back to you!

Actual calculation is 50cm x 1.5 = 75cm.

To get 150cm it would be 50cm x 3.

Isn't it just: one times as long and half as long added together
So one times as long = 50cm
half as long = 25cm
Therefore one and a half times as long = 75cm

I think the confusion is in the wording 'as long', ie an english problem, not a maths problem!

I think in this case it would be 75

If it said something like 'one and a half times as long again' then I would add in the original 50 to make 125

It is 75cm, or given the fraction in the question, 3/4 of a metre long.
The important line in the question is "one and a half times as long " if it had said "one and a half times longer " it would be 125cm (or 1 1/4 metres) IYSWIM

just seen the teacher said 150, so not sure where she got that from - very embarrassing!

Yes. That is the answer I came to.

It is the words "as long" that threw me because I would say that is half as long again. Whereas it almost reads as if they're saying 1 1/2 times longer.

So the basic "sum" in this IS 50 x 1.5? = 75.

Bloody Maths tests.

And you mustn't say 'sum' - that only refers to addition.

Sorry.

The basic calculation...... .

That's better!

75cm. What age would be expected to answer that, out of interest OP?

75cm - 1 and ½ times longer just means wood x 1.5.

75cm..............................and a rubbish teacher.