Question

An Amount of $ 14400 is made up of $100, 50, 20 and 10 notes. The number of $10 notes are 3 times the number of 20 notes. The number of $20 note are 5 times the number of $50 notes.
The number of $50 note are 5 times the number of $100 notes. How many of $100 note are there?

Answer 1

Let the amounts of notes be u,v,w,x respectively. Now just start writing down the facts:

100u+50v+20w+10x = 14400
x = 3w
w = 5v
v = 5u

Now just solve for u.

Or, consider if there is a single $100 note. That means there are 5 $50's, 25 $20's, 75 $10's

100+5*50+25*20+75*10 = 1600
9 * 1600 = 14400

So, there are 9 $100's, and 9 times as many of the others shown above.