A punctuation ambiguity crept in in 412 (ii). The revised question 412 (ii).

412. A bag contains 5 red balls, 8 white balls, 4 green balls, and 7 black balls. If one ball is drawn at random, find the probability that it is

(i) black

(ii) red

(iii) not green.

#413. If a letter is chosen at random from the word

(i) TRIANGLE

(ii) RECEIVE

what is the probability that it is a vowel?

Special Thanks for second one.

]]>EVW's answers are also not adequate. This is not her fault. The question as written is very ambiguous. One thing you must always state in the problem whenever you are drawing from a list of numbers, a bunch of urns with balls in them, a deck of cards... is whether or not it is with replacement or not. Please see EVW's post for an explanation of those terms. If you need more please ask.

]]>2A x AB = 1971, A =B, find a + b.

where does it fit in ?

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