Chocoholics

This means the chocolate bar is less than 100p but more than 50p.

C	J	G	Total
100p	50p	98p	148p	Too much
70p	20p	68p	88p	Too much
50p	0p	48p	48p	Could be right
51p	1p	49p	50p	Could be right
52p	2p	50p	52p	Too much
53p	3p	51p	54p	Too much

So the right answer is either 50p or 51p. If Jim definitely has some money, then the cost of the chocolate bar is 51p.

Well done, Jack. Luke from St. Nicolas Junior School, Newbury reasoned his way through the solution :

George needs 2p more, so Jim must have less than 2p because otherwise, he would have given George the 2p he needed. So I chose 1p for Jim. As Jim needed 50p more, the chocolate bar must cost 51p.

Jim	Cost of chocolate bar	George
1p	51p	49p

Add George's money and Jim's money, which is 50p, so they still don't have enough to buy the chocolate bar together. Another solution I found was:

Jim	Cost of chocolate bar	George
0p	50p	48p

Similarly Jim has J pence and choc costs J + 50 pence.

Say C = J + 50 or J = C - 50.

If their total money is less than cost of a bar then G + J is less than choc bar.

So G + J < C which is the same as (C - 2) + (C - 50) < C.

This simplifies to 2C - 52 < C and further to C < 52.

So the choc bar costs less than 52p but George has 48p more than Jim.

So the only possibility is for George to have 49p, Jim 1p, their total is 50p and the choc bar must be 51p (as we showed above it must be less than 52p).