Question

for this question do you divide?

Answer 1

A weather balloon holds 2,850 cubic meters of helium. The density of helium is 0.1685 kilograms per cubic meter. How many kilograms of helium does the balloon contain? Please round your answer to the nearest whole number. Only enter a numerical value in the answer blank.

Answer 2

you would divide 2850 / 0.1685?

Answer 3

If you knew the mass and volume, you divide to get the density. However, we don't know the mass which is why we end up multiplying instead (think of it as undoing division)


Density = mass/volume

D = m/v

0.1685 = m/2850

0.1685*2850 = m ... Multiply both sides by 2850 to isolate m

m = ??.

Answer 4

i got 480.225

Answer 5

is that correct?

Answer 6

@jim_thompson5910

Answer 7

I'm getting the same. Then you round to the nearest whole number.

Answer 8

so 480

Answer 9

can you check one more question?

Answer 10

sure

Answer 11

The population of Tinyville is 16.2 Tinys per acre. Exactly 405 Tinys live in Tinyville. How many acres is Tinyville? Only enter a numerical value in the answer blank.

Answer 12

i got 0.04

Answer 13

should i have multiplied?

Answer 14

population density = (# of people total)/(total area)

Answer 15

population density = 16.2 Tinys per acre
# of people total = 405 tinys
area = unknown

Answer 16

let x = unknown area

population density = (# of people total)/(total area)
16.2 = 405/x
x = ??

Answer 17

i got 25 0.0

Answer 18

25 acres is correct

Answer 19

hopefully that's a face after the 25? and it's not two hundred fifty point zero?

Answer 20

yeah its a face lol

Answer 21

I thought so but wasn't sure lol

Answer 22

one way to keep things straight about multiplying or dividing is to use ratios
when you see
"16.2 Tinys per acre"
read
16.2 Tinys per 1 acre"
and the word "per" read as "divided by"
that is, write the ratio
\[ \frac{ 16.2 \ Tiny }{1 \ acre} \]

Next they say:
Exactly 405 Tinys
... x (unknown acres)
write another ratio of # of Tiny's divided by number of acres
\[ \frac{ 16.2 \ Tiny }{1 \ acre} = \frac{405}{x} \]
now you "solve for x"

Answer 23

the first trick, is if the x is in the bottom, you can "flip" both sides
\[ \frac{1 \ acre} { 16.2 \ Tiny }= \frac{x}{405 \ Tinys} \]
now to "solve for x"
multiply both sides by 450 Tinys
\[ \frac{1 \ acre} { 16.2 \ Tiny } \cdot 450 \ Tinys= \frac{x}{405 \ Tinys} \cdot 450 \ Tinys\]
and that simplifies to
\[\frac{ 450}{16.2} \ acres= x
\]