7. Ingredients For six people For twelve people Division
squid 200 grammes 400 grammes 400:200 = 2
prawns 300 grammes 600 grammes 600:300 =2
clams ½ kilo 1 kilo 1 : ½ = 2
crabs ¼ kilo ½ kilo ½ : ¼ =2
mussels ¼ kilo ½ kilo ½ : ¼ =2
rice 600 grammes 1200 grammes 1200:600 = 2
cups of water 2 ½ 5 5 : 2 ½ = 2
12 people : 6 people = 2
SPREADSHEET
8. Ingredients For six people For nine people
squid 200 grammes 200 *1.5=300grammes
prawns 300 grammes 300*1.5=450 grammes
clams ½ =0.5 0.5*1.5=0.75 =3/4 kilo
crabs ¼ =0.25 0.25*1.5=0.375 =3/8 kilo
mussels ¼ =0.25 0.25*1.5=0.375 =3/8 kilo
rice 600 grammes 600*1.5=900 grammes
cups of water 2 ½=2.5 2.5*1.5=3.75
9 people : 6 people = 1.5
SPREADSHEET
9. Other examples of direct proportionalityOther examples of direct proportionality
If an object travels at a constant speed, then the
distance traveled is proportional to the time spent
traveling, with the speed being the constant of
proportionality.
On a map drawn to scale, the distance between any
two points on the map is proportional to the distance
between the two locations that the points represent,
with the constant of proportionality being the scale of
the map.
10. THE RULE OF THREE (Direct)THE RULE OF THREE (Direct)
First, write the titles of
the two magnitudes
Second, place the
quantities you know in
their correspondent
column
Third, write an x for the
unknown quantity.
Last, multiply in cross,
make equal the terms,
and find the x.
6
4 0,5 kilo
x
TAPSINVERSE
11. People Sweets
24 2
12 4
6 8
Number of sweets in the bag= 48
Inverse ProportionalityInverse Proportionality
12. Inverse ProportionalityInverse Proportionality
Some examples:
Magnitude A Magnitude B Proportionality
constant
speed time spent traveling distance of the
journey
number of people
working
number of working
days
working days for an
only worker
price of sweets number of sweets I
can buy
my money
13. Inverse ProportionalityInverse Proportionality
(24 very small prawns in the paella)(24 very small prawns in the paella)
For four people
For six people
For seven people
Six prawns for each
one
Four prawns for each
one
Three prawns and a
half for each one
(aproximately)
14. THE RULE OF THREE (Inverse)THE RULE OF THREE (Inverse)
First, write the titles of
the two magnitudes
Second, place the
quantities you know in
their correspondent
column
Third, write an x for the
unknown quantity.
Last, multiply in line,
make equal the terms,
and find the x.
4 6
x8
15. A summertime problemA summertime problem
Now it’s noon. It’s boiling.
The pool is empty!
So, we want to fill it.
16. At the poolAt the pool
Two taps
Tap A fills the pool in 3 hours
3 hours
Tap B fills the pool in 6 hours
6 hours
17. At the pool (and after, theAt the pool (and after, the
paella)paella)
So, if in an hour, we fill a half of the pool, it’s evident
that we will need two hours to fill completly the
pool.
Solution: 2 hours later, at 2 P.M.
Editor's Notes
It may not be 24 prawns in a quarter kilo, but less.
