a How many seats are there on the carousel in total?
B
b $1= 100 pennies, $1= 20 nickels and $1 = 10 dimes.
C
c What can you actually roll with a regular die?
D
d How many shaded regions are there?
A
a P(horse)≈ 33 %
P(unicorns)=12.5 %
P(zebra)=6.25 %
B
b P(dime)≈ 7.69 %
C
c P(rolling an 8)=0 %
D
d P(hitting a shaded area)≈ 56 %
Practice makes perfect
a To calculate the probability of randomly picking a horse, a unicorn and a zebra, we have to divide the number of these animals on the carousel with the total number of animals on the carousel. We will assume that all seats are available for little Eric to choose from.
r|c
giraffes & 4
lions & 4
elephants & 2
horses & 18
monkey & 1
unicorns & 6
ostriches & 3
zebras & 3
gazelles & 6
dinosaur & 1By adding these numbers, we get the total amount of animals (or seats) on the carousel.
4+4+2+18+1+6+3+3+6+1=48
Now we can calculate the probability that we pick one of the desired animals. To express it as a percentage, we calculate the fraction and then multiply the quotient by 100.
P(horse)&=18/48=0.33333...≈ 33 % [1em]
P(unicorns)&=6/48=0.125 = 12.5 % [1em]
P(zebra)&=3/48=0.0625=6.25 %
b To find the probabilities, we first have to determine how many coins Eduardo has. Below we show how many pennies, nickels and dimes equals $ 1.
$1 &= 100 pennies
$1 &= 20 nickels
$1 &= 10 dimesBecause Eduardo has the equivalent of $ 1 for each type of coin, we can determine the total number of coins in his pocket.
100+20+10=130 coins
Now we can calculate the probability that Eduardo pulls out a dime by dividing the number of dimes with the total number of coins.
P(dime)&=10/130=0.07692...≈ 7.69 %
c On a regular die you can score 1, 2, 3, 4, 5, and 6. Therefore, rolling an 8 on a single role is an impossibility. Thus the probability of this happening is 0 %.
d To find the probability of hitting a shaded region, we need to determine the total number of shaded regions. Let's count them up.
There is a total of 5 shaded regions. From the diagram we count an additional 4 white regions which means the total number of regions, shaded and unshaded, is 5+4=9.
P(shaded region)&=5/9=0.55555...≈ 56 %
