How would you explain this?

11 Plus Maths – Preparation and Information

Moderators: Section Moderators, Forum Moderators

Post Reply
11 Plus Platform - Online Practice Makes Perfect - Try Now
Manana
Posts: 710
Joined: Wed Mar 09, 2011 3:22 pm

How would you explain this?

Post by Manana »

It's from the Heinemann 6 word problems book.

I am half-way halfway between 2 consecutive numbers. The product of the two numbers is 650.

I presume the two numers are 25 and 26 (by finding the square root of 650), making the 'half way' number 25.5?

How would you calculate this without a calculator though? ;)
sgcmum
Posts: 182
Joined: Sat Oct 09, 2010 11:46 am

Re: How would you explain this?

Post by sgcmum »

You could factorise and combine I.e 650= 10*65 =5*2*5*13 =5*5*13*2 = 25*26
Giving you the answer 25.5

Sgcmum
Stocky
Posts: 391
Joined: Mon Aug 22, 2011 1:12 pm

Re: How would you explain this?

Post by Stocky »

I like sgcmum's method alot. Another way I use is think in 10's. 20x20=400, 30x30=900, its between there. Go half way i.e. 25x25=625 (closer but still lower), 26x26=676 (closer but now higher) so that's it gotta be 25 and 26.
mystery
Posts: 8927
Joined: Tue Jul 21, 2009 10:56 pm

Re: How would you explain this?

Post by mystery »

Or you'd solve a quadratic equation?

x ( x +1 ) = 650

x2 + x -650 = 0

Then solve as usual.

The answer would be halfway between x and x+1. Would quadratic equations be expected for this particular Heinemann paper?
mystery
Posts: 8927
Joined: Tue Jul 21, 2009 10:56 pm

Re: How would you explain this?

Post by mystery »

oops sorry that would need a calculator too. Does it need to be done without a calculator? If so, the other methods win.
yoyo123
Posts: 8099
Joined: Mon Jun 18, 2007 3:32 pm
Location: East Kent

Re: How would you explain this?

Post by yoyo123 »

I wouldn't expect quadratic equations for yr 6
daveg
Posts: 247
Joined: Thu May 10, 2012 9:30 am

Re: How would you explain this?

Post by daveg »

Manana wrote:It's from the Heinemann 6 word problems book.

I am half-way halfway between 2 consecutive numbers. The product of the two numbers is 650.

I presume the two numers are 25 and 26 (by finding the square root of 650), making the 'half way' number 25.5?

How would you calculate this without a calculator though? ;)
I wonder if -25.5 would be marked correct?
Post Reply
11 Plus Mocks - Practise the real exam experience - Book Now