
By: Tping (offline) Monday, March 25 2013 @ 07:22 PM CDT (Read 1343 times)



Tping 
Hi, please help..
At Station A, the ratio of the number of children to the number of adults on a train was 4:5.
At the next station, 12 children alighted and 10 adults boarded the train.
The ratio of the number of children to the number of adults on the train then became 7:10.
How many children were on the train at first?
Thank you.

Junior
Registered: 01/26/12 Posts: 25





By: angeliakwok (offline) Friday, March 29 2013 @ 08:22 PM CDT



angeliakwok 
This concept is usually called external change, as the change values changes the end ratio units.
LCM the end ratio units to create an equal stage, as you would in simultaneous change
(C4u  12 = 7p) x 10
(A5u + 10 = 10p) x 7
C40u  120 = 70p
A35u + 70 = 70p
therefore
5u is 120 + 70 = 190
1u is 38
Children at first is 4 x 38 = 152
apologies I draw models but i dont how to do it with this app

Newbie
Registered: 02/17/11 Posts: 5





By: T0116060A (offline) Saturday, August 10 2013 @ 11:36 PM CDT



T0116060A 
This sum is actually (EVERYTHING CHANGES)
Now, do you know how to do this sum?
If you don't know how to do this sum, please clarify with me or Edward.....
Thank you!

Newbie
Registered: 08/10/13 Posts: 10



