# maths

posted by .

1. A die labelled A has one face marked 1, one face marked 2 and the other four faces marked 3. A die labelled B has four faces marked 2 and two faces marked 3. The dice A and B are thrown. Calculate the probability is 5.

I got 18/36

2. There are 12 boys and 20 girls in a class. 25% of boys and 25% of girls study physics; What is the probability that a student chosen at random is a girl studying physics.

I found that 3/12 boys therefore study physics and 5/20 girls therefore study physics. So 9/12 and 15/20 don't study. I'm not sure what to do next...add? multiply?

3. Calculate the probability that there are fewer boys than girls in a family of 6 children if the probability of have a boy is 1/2.

?

4. There are 6 nesting boxes in a garden. The probability of one nesting bow being occupied is 0.7%; Calculate the probability that at best 5 boxes are occupied.

Therefore 99.3% not occupied ...

Could someone please read through my work and help if possible. I know there are 4 questions its more advice/tips and is this right?
Thanks for any help! :-)

• maths -

1) Yes, agree 18/36 but that is 1/2
1/6*2/6 + 4/6*4/6 = 2/36+16/36 = 18/36 = 1/2

2) 5 girls take physics. There are 32 students so 5/32

• maths -

0, 1, 2 boys out of 6
binomial distribution
p(k) = C(n,k) (1/2)^k * (1/2)^(n-k)

p(0 boys) = C(6,0) (1/2)^0 (1/2)^6
= (1/2)^6 = 1/64

p(1 boy) = C(6,1)(1/2)^1 (1/2)^5
= 6 (1/2)(1/32)
= 6/64

p(2 boys)= 15 etc

If you do not use Pascal's triangle, the formula for C(n,k) is:
n! / [ k! (n-k)! ]

• maths -

5) I THINK YOU MEAN 0.7, NOT .7%

Do binomial distribution again but this time for 1 out of 6 unoccupied

Probability of any box being empty = .3

Probability of exactly 1 out of 6 being empty
= C(6,1)(.3)^1 (.7)^5
= 6 * .3 * .16807

• maths -

Oh, and subtract that from one to get the probability of 1, 2, 3, 4 or 5 being occupied, but not all six.

• maths -

If a family already has three girls, what is the probability that the next child will be a girl?

## Similar Questions

1. ### Math(Probability)

Let X and Y equal the outcomes when two fair six-sided dice are rolled. Let W = X + Y. Assuming independence, find the p.m.f. of W when (a) The first die has three faces numbered 0 and three faces numbered 2, and the second die has …
2. ### math

on november 1, the holiday house store marked up a \$50 decoration by 30%. On November 28, the decoration was marked down 10%. It was marked up 20% on sales on December 1. Finally it was marked down 70% on December 26. Find the final …
3. ### maths

A die has one red face, two blue faces, and three green faces. It is rolled 5 times. Find the chance that the red face appears on one of the rolls and the remaining rolls are green.
4. ### Maths

Cam and Dean are playing a game with counters and dice. Cam has some counters, each labelled 1 on one side and 2 on the other. He flips the counters and scores the total of all the numbers showing. Dean has one die and scores the number …
5. ### math

A specially made pair of dice has only one- and two-spots on the faces. One of the dice has three faces with one-spot and three faces with two-spot. The other die has two faces with one-spot and four faces with a two-spot. One of the …
6. ### math

A specially made pair of dice has only one- and two-spots on the faces. One of the dice has three faces with one-spot and three faces with two-spot. The other die has two faces with one-spot and four faces with a two-spot. One of the …
7. ### math

On a standard six-faced die,the numbers of the opposite faces always add to seven,Dena rolls a pair of fair,standard six-faced dice.She then takes the product of four numbers ,the two numbers on the faces that are showing on top of …
8. ### Maths

Two tetrahedral dice are thrown; one is red and the other is blue . The number on which each lands is noted, the faces being marked 1,2,3,4. Find the probability that the sum of the numbers on which the dice lands is 6 given that the …
9. ### math

Six slips of paper, with a different digit from 1 to 6 printed on each, are placed in a box. The papers are well mixed. One slip is drawn and replaced. The papers are well mixed, and a second slip is drawn. Find the probability of …
10. ### math

The faces of a green tetrahedron die are marked 10,20,30 and 40. All three die are thrown together and the scores added. Find the probability that the total is more than 30 but less than 35.

More Similar Questions