part (a) cant be solved

part (b) can be solved.

Isn't (b) related to (a)? If (a) can't be solved, why (b) can be solved?

Use the net change of number of people. For ratio, use 5:7 and 7:13

Both parts of the question can be answered, but part (b) must be determined before part (a) can be revealed. Let me write out the solution to be posted later.

yah true

Part (a) can be answered. Since the ratio of the adults to children entering the event hall is the same as the original (i.e. 5:7), therefore the new ratio of adults to children will still be 5:7 (Unchanged).

Desmond Tan excellent observation, Kudos.

oh yah.... 60:84 can be simplified to 5:7

So (a) still 5:7? We don't hv to bother the original ratio of 5:7? (b) is it 490 children in the hall at first?

For (a) since the original ratio is 5:7 and the ratio of adults to children entering the hall is also 5:7, the ratio of the adults to children in the hall now will still be 5:7. For (b), the answer should be 63 children.

Thanks all

Happy to help. Regards.

All the Maths Gurus!

I don't speak for the rest but I am certainly not a maths guru. I have learned plenty from the contributors here.

Is the answer $300 ?

Thanks! I don't have the answer yet but I'll go with your suggested answer & workings!!👍😊

I hope it's correct !

Let Jess have at first to be 100u... Spent-40u(40%)+$30 Remainder--60u-$30 Spend 36u-$18(60% of the remainder) $15 spend on CD's TotalSpent----- 40u+$30+36u-$18+$15 ==76u+$27 Balance will be 100u minus 76u+$27 === 24u-$27 24u-$27= $45 24u° = $72 u=$3.... 100u= $300(answer)

Xavier - By drawing model, they can understand better.

I beg to differ. I worked backwards and used simple reasoning to arrive at this answer. 

Thx Raymond Ng

Sorry, not D but V. C for car and V for van..

Thanks Pauline Vong

Raymond Ng, very simple and concise.

a. (Quarter of a perimeter of big circle + twice the length of the big square) + (perimeter of the semi circle + twice the length of point A to B).