puzzled

can anyone help me with a probability question?

Of all the videotapes in a large shipment, 21% have a defective tape, 16% have a defective case, and 11% have both defects. If you purchase one of the videotapes in this shipment, find the probability that it has the following. (a) A defective tape or a d...

A stock solution of ethanol is made by weighing out the correct amount of absolute ethanol in a tared beaker containing 15 ml of water. Why is it necessary to add water to the beaker before adding the ethanol?

I bought 10 bananas. Each banana weighed 50 grams. If the price for bananas was $6.50 per kg, how much did I pay?

a box containing 4 identical books weighs 5kg. If the weight of the box is 600g, what is the weight of each book?

I bought 10 bananas. Each banana weighed 50 grams. If the price for bananas was $6.50 per kg, how much did I pay?

Thank you Ms. Sue!! :)