In jar A there are 3 white balls and 2 green ones, in jar B there is one white ball and three green ones. A jar is randomly picked, what is the probability of picking up a white ball out of jar A?
Answer(s): C
The probability of picking the first jar is ½, the probability of picking up a white ball out of jar A Is 3/(3+2) = 3/5. The probability of both events is 1/2 x 3/5 = 3/10.
The probability of pulling a black ball out of a glass jar is 1/X. The probability of pulling a black ball out of a glass jar and breaking the jar is 1/Y. What is the probability of breaking the jar?
Answer(s): B
Let Z be the probability of breaking the jar, therefore the probability of both events happening is Z x (1/X) = (1/ Y). Z = X/Y.
An ant walks an average of 500 meters in 12 minutes. A beetle walks 15% less distance at the same time on the average. Assuming the beetle walks at her regular rate, what is its speed in km/h?
Answer(s): A
A beetle moves (0.85 x 500 = 425 meters) in 12 minutes that is equal to 0.425 Km in 1/5 of an hour. The speed in the right units is 0.425 x 5 = 2.125 Km/h.
A car was driving at 60 Km/h for 20 minutes, and then at 90Km/h for another 40 minutes. What was its average speed?
The average speed is equal to: (Total distance)/(Total time) = (60 x 1/3 + 90 x 2/3)/1 = 80 Km/h.
The distance from Steve’s house to work is 30 Km. On the way back Steve drives twice as fast as he did on the way to work. Altogether, Steve is spending 6 hours a day on the roads. What is Steve’s speed on the way back from work?
Answer(s): E
Steve’s speed on the way back is double the speed to work therefore it takes him half the time to return home ---> Divide 6 hours by 1:2 ratio, the time it takes him to get home is 2 hours and the time driving to work is 4 hours. 30 Km in 2 hours is 15 Km per hour.
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