8.23 America[转自我看机警]

smart

1.10-pounds sample,5% is metal, the rest is rock. the metal
is composed of gold and silver. silver is 10 times as much gold. ask: what is the gold's weight?
2.n persons is surveyed about looking A newsletters and B newsletters. the number of seeing a is x% and the number of seeing B is y%, the number of seeing both A and B is z%,. ask:what is the number of not seeing A and not seeing B?(n,x,y,z is told. I don't remember clearly)
answer: n*(1-x%-y%+z%)
3.in the following equations, which has exactly one point that has the whole number of both x-coordinate and y-coordinate?
A. B. C. D. Y=X+1/2 E.Y=(the square root 3 )*x
answer: E
4.completing an order, machineA need x hours solely, machineB need y hours solely. ask: if machineA and machineB
work together, how many hours comleting 1/2 of this order?(x,y are told)
5.A motorist travel from X to Z. Y is one point douring this
trip(from X to Y). The average speed from X to Y is 15 miles
per second. ask: what is the average speed from Yto Z?
(1). the average speed from X to Y is 10 miles per second
(2). the tome from Y to Z is 20 seconds.
my answer: E