To ask for help with maths

[craftycrochet]

DD homework

Using + and x only and all the numbers once make 129 from

3 6 7 9 10

We've been trying for an hour and cannot get it. Closest was 130. Any ideas? Or is it a sneaky trick question to get you doing lots of maths as there is no answer!!

Definitely no - or divide?

6x7=42
10-9 = 1
42+1=43
43x3=129

But that uses a minus sign. I'll keep trying.

9x10=90
6+7=13
13x3=39
90+39=129.

I can only do it Teen's way too!y

6+7 = 13

13 x 3 = 39

9 x 10 = 90

90 + 39 = 129

Hurrah!

I'm a maths teacher (secondary) and I hate these! It takes me ages to see the answer and the kids are often quicker than me. Just posting to say don't feel stupid for not being able to figure it out!

paper I agree. It is just depressing to take an hour and not solve it. There isn't a clear logical step by step, it's just teaching guesswork.
Fine for an able child with quick mental maths, my DDs would have just found it frustrating.

Thank you so much! DD isn't a maths fan and stuff like this does not go down well with her. Frustration is right. Happy DD now tho

(3+7+10)=20, 20x6=120, 120+9=129

So that's ((3+7+10)x6)+9 = 129 in one go

Ooh I like it Arkestra More elegant.

As fans of Rachel Riley will know, you need to do a degree in maths to get good at these (because obviously the degree course is three years of doing successively harder sums... ).

Uggh I gave up. Though I suppose it’s not total guesswork as there as limited ways to get a number ending in 9, which logically restricts the options.

67=42
10-9=1
Add them together
433=129

Never be embarrassed to use Excel for these sorts of questions. Trying all possible combinations can become a lot easier.

slash Unfortunately you subtracted but it isn't allowed.

Come on, Teen, this is lightweight stuff. Over on that probability thread, we're summing infinite series, and I may have invoked the Central Limit Theorem....

This is all I'm good for these days.
Anything past GCSE does my head in.