Question

Human hair grows at a rate of approximately three-twentieths centimeters per year. How many centimeters does it grow in two-thirds of a year?

one-tenth centimeters

forty-nine sixtieths centimeters

nine-fortieths centimeters

thirty-one sixtieths centimeters

Answer 1

@phi can you help me please if you can

Answer 2

can you write a ratio ?

Answer 3

@phi well I have trouble with ratios

Answer 4

another way is use

rate * time = distance (or "growth" in this case)

what is the rate ?
what is the time ?

Answer 5

rate: \[\frac{ 3 }{ 20 }\]

time: \[\frac{ 2 }{ 3 }\]

Answer 6

yes, but you should put in the units. now multiply rate * time
\[ \frac{3 \text{ cm}}{20\cancel{\text{ yr}}} \cdot \frac{2}{3} \cancel{\text{yr}}= ?\]

Answer 7

@phi ok.. so what do I do..?

Answer 8

multiply rate * time

Answer 9

ok hold on a second

Answer 10

it gives me 0.1 which is 1/10

Answer 11

and 1/10 is one of my answer choices so that the answer right?

Answer 12

yes.

when you multiply fractions, you multiply top times top and bottom times bottom
\[ \frac{3 \cdot 2}{20 \cdot 3 } \]
notice you can divide top and bottom by 3 (it's easier to simplify first)
you get
\[\frac{2}{20} \]

now notice you can divide top and bottom by 2 to simplify more. you you get
\[ \frac{1}{10} \text{ or } 0.1 \]

Answer 13

and the answer is 0.1 cm or 1/10 cm

Answer 14

ty