s1 probability help!

d Given that this student is right-handed, find the probability that the student is studying Science subjects.

So, you're looking for the fraction of the number of students that are "right-handed and study science" over the total number of students that are "right-handed".
(Not worded very well....)

Can you take it from there?

I wrote =

[30/148 + 0.743 ] / (110/148)
=1.27 which is incorrect according to the textbook . why??? @@ correct answer: 0.218

thank you!

I wrote =

[30/148 + 0.743 ] / (110/148)
=1.27 which is incorrect according to the textbook . why??? @@ correct answer: 0.218

thank you!

OK. Where did you get those figures from? What do they represent?

You're looking for "Number of righthanded science students" / "number of righthanded students"

I've done mine as whole numbers rather than decimals but hopefully you get the idea. Q


Posted from TSR Mobile

One more question :when there is ten balls , 5 red 3 blue others are white , draw three balls from the bag, what is the probability that two balls are red in colour. Is there one method that {RRX}+ {RXR}+ {XRR}, where x can be blue or white, and I havr to multiply thr probability by 3??

Yes, you only need to work out {RRX} and multiply by 3, as they'll all have the same probability.

actually why I must multiply the probability by 3? can you explain the logic behind it?

You can either work out the three probabilities separately {RRX} + {RXR}+ {XRR}, or work out one of them and multiply by 3, as they're mumerically all the same.

Order is important here - RRX is a different selection to RXR, and to XRR.