please help ASAP. I don't understand this

you have 2450 bills each of which has the value of one dollar and they altogether weigh 5 pounds. so each dollar weighs
[tex] \frac{5}{2450} \: \: pounds[/tex]
now if get a stack of 1470 bills, they should weigh
[tex]1470 \times \frac{5}{2450} = 3 \: \: \: pounds[/tex]