Question

A 2-lb bag of brown rice costs five dollars. How much would you expect to pay for a ten-lb bag of brown rice, assuming there is no discount for buying a larger bag?

Answer 1

@smartone

Answer 2

@TheSmartOne

Answer 3

hi, i really need help

Answer 4

do you know about ratios or proportions?

Answer 5

yes

Answer 6

write down the ratio of $/pounds for the one you know
then write down the ratio for the one you don't know
(use x for the part you don't know)

and set them equal

can you do that ?

Answer 7

the ratio of dollars to pounds is 5 to 2

Answer 8

or 5:2

Answer 9

or 5/2

Answer 10

yes , write that as a fraction
yes 5/2 = the other ratio

Answer 11

ok

Answer 12

can you write the other ratio? (use x for the unknown cost)

Answer 13

soooo... ummm 5/2= x ?? sorry i really suck at math

Answer 14

the other ratio is also dollars/pounds

you know the pounds, right? but you don't know the dollars (so use x for the dollars)
can you write the second ratio?

Answer 15

ohhhh so would it be 10 to x ?

Answer 16

or 10/x

Answer 17

or 10:x

Answer 18

you want the *same* order as the first ratio. x dollars/ 10 pounds to match
5 dollars/ 2 pounds

Answer 19

oh my bad so x/10

Answer 20

yes, now set the ratios equal to each other

Answer 21

you should get
5/2 = x/10

Answer 22

yes i was just typing that lol

Answer 23

now to find x, the fastest way is to multiply both sides by 10
\[ \frac{5}{2} \cdot 10 = \frac{x}{10} \cdot 10 \]

notice on the right side, that is the same as
\[ \frac{5}{2} \cdot 10 = x\cdot\frac{10}{10} \]
and 10/10 is 1
and 1*x is just x, so you get
\[ \frac{5}{2} \cdot 10 = x \]

Answer 24

oh ok

Answer 25

can you find what x is ?

Answer 26

oh duuh yeah

Answer 27

its 25

Answer 28

get the idea?

write down the ratio of the part you know
write down the ratio (in the *same order* e.g. dollars/pound in this case)
use "x" for the part of the ratio you don't know.
set the ratios equal to each other
solve for x

Answer 29

oh yeah i do ! thanks so much for your help:D I understand it now!

Answer 30

btw, if you end up writing

2/5 = 10/x (which is ok, this is pounds/$ = pounds/$ )
to solve for x, you can first "flip" both sides to get
5/2 = x/10

now solve for x by multiplying both sides by 10

Answer 31

oh ok i understand. :) thx again @phi