11 Plus Exams Forum

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?

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

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.

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?

oops sorry that would need a calculator too. Does it need to be done without a calculator? If so, the other methods win.

I wouldn't expect quadratic equations for yr 6

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?