1. Hence, factorize ( 2a^2 - 18 ) - (3b - ab ).
2. A bag contains some coins as shown below :
Coin | $0.5 | $1 | $5
Number | 16 | 24 | 10
If a coin is chosen at random, find
(a) the probability of getting at least one dollar.
(b) the expected value of the coin.
math problems~help!!!!
2007-12-08 1:40 pm
回答 (1)
2007-12-08 5:03 pm
✔ 最佳答案
(2a^2 -18) - (3b - ab)=2(a^2 - 9) - b(3 - a)
=2(a + 3)(a - 3) + b(a - 3)
=(a - 3)[2(a + 3) + b]
=(a - 3)(2a + b + 6)
There are 16 + 24 + 10 = 50 coins total and there are 24 + 10 = 34 coins at least worth a dollar ( the 1 dollar and 5 dollar coins) so the probability of at least 1 dollar is 34/50 = 0.68
The expected value = sum of the values of the coins times its probability.
So it is = ($0.5 x 16/50) + ( $1 x 24/50) + ($10 x 10/50)
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