help needed with probability question, age question and 'zap
Posted: Thu Aug 27, 2009 12:18 pm
I am struggling with this type of question:
I can explain P of 1 green being 7/18 etc but have become stuck
1) there are 6 red, 7 green and 5 blue beads in a bag. What is the smallest number of beads taken out before i can be sure of getting at least 2 of each colour?
Ans. 15
2) In 6 years' time Mira will be twice as old as she was 3 years ago. How old is she now?
Ans. 12
why can't I do
now x-6 = 2(x+3)
x-2x = 6+6
-x = 12
3) what is the quickest way - what are they testing in this sort of question
a number can be zapped by mulitplying its digits so 235 zapped is equal to 2x3x5 = 30.
what is the smallest number which can be zapped to give 24?
Many thanks for your help; i have tried or hours especially with probability and age question.
feeling quite out of all this
I can explain P of 1 green being 7/18 etc but have become stuck
1) there are 6 red, 7 green and 5 blue beads in a bag. What is the smallest number of beads taken out before i can be sure of getting at least 2 of each colour?
Ans. 15
2) In 6 years' time Mira will be twice as old as she was 3 years ago. How old is she now?
Ans. 12
why can't I do
now x-6 = 2(x+3)
x-2x = 6+6
-x = 12
3) what is the quickest way - what are they testing in this sort of question
a number can be zapped by mulitplying its digits so 235 zapped is equal to 2x3x5 = 30.
what is the smallest number which can be zapped to give 24?
Many thanks for your help; i have tried or hours especially with probability and age question.
feeling quite out of all this