F.5 MATHS ......

yan

2011-01-01 9:34 pm

1. The base radius and slant height of a soild right circular cone are r cm
and (r+3)cm respectively.If the total surface area of the cone is not less
than 35兀 cm^2 , find the range of values of x

ANS r>=3.5

2.Among the 45students who join an English tutorial class or a Mathematics tutorial class,35 students join the English tutorial class and
25 students join the Mathematics class.A student is chosen at random from these 45 students.Find the probability that the student chosen joins both the English tutorial class and the Mathematics tutorial class.

ANS 1/3

回答 (1)

ShingMingTony

2011-01-01 9:51 pm

✔ 最佳答案

1. The base radius and slant height of a soild right circular cone are r cm
and (r+3)cm respectively.If the total surface area of the cone is not less
than 35pi cm^2 , find the range of values of r

35pi =< r(r+3)pi + r^2*pi
2r>=7
r>=3.5

2.Among the 45students who join an English tutorial class or a Mathematics tutorial class,35 students join the English tutorial class and
25 students join the Mathematics class.A student is chosen at random from these 45 students.Find the probability that the student chosen joins both the English tutorial class and the Mathematics tutorial class.

join English = E, join Mathematics =M
[E∩M] = [E] + [M] - [E∪M] = 25+35-45=15
P[E∩M] = 15/45=1/3

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