ratio question

[Menthol]

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$1 is eqaul to 7 drachmas and that 5 drachmas is equal to 3 quilos. What is the ratio of dollars to quilos

so what I did is
since $1= 7drac and 5drach= 3quilos
$1/7=1 drac and 1 drach=3/5 quilos

(1/7)/ (3/5)= 5/21
but the answer is 21/5 🙁

thank yoU!

 

[NhuPT]

I actually don't like how Math Destroyer explains certain problems.
But here is what I would do:

$1 --> 7D
5D --> 3Q ---> D = 3/5Q

Substitution: $1 --> 7(3/5Q)
$1 --> 21/5 Q

 

[kc1469]

$1 is eqaul to 7 drachmas and that 5 drachmas is equal to 3 quilos. What is the ratio of dollars to quilos

so what I did is
since $1= 7drac and 5drach= 3quilos
$1/7=1 drac and 1 drach=3/5 quilos

(1/7)/ (3/5)= 5/21
but the answer is 21/5 🙁

thank yoU!

I feel your pain with this question. The way its worded had me completely lost and I searched the internet for an hour when I was studying for the DAT to figure out how to do this question and this is the best way to look at it.

So you know 1$=7D & 5D=3Q.
Your right by setting one of the variables in terms of the other. We want the ratio of dollars:quilos.
So lets get D in terms of Q. --> D= 3/5Q (as you did above).
Plugging in, we get:
1$= 7(3Q/5)=21Q/5.
Getting to here is easily done. Now comes the tricky part. We want the RATIO OF DOLLARS:QUILOS.
We have: 1$=21Q/5... Q is in the numerator---> MULTIPLY both by (1/Q).
We now have:
$/Q= 21/5 OR the ratio of dollars to quilos is 21/5.

 

[aqz]

Omg all of yall with your crazy substitutions....have you guys never learned "mole to mole" ratio?

All you gotta do is some simple stoichiometry....

1 dollar * (7 drachmas/1 dollar) * (3 quilos/5 drachmas)

Cancel out all the units there:

= 21/5 quilos

Frankly, I want to know if you're okay with gen chem problems.