John had $21 to spend on 2 notebooks. after buying them he had $13. how much did each notebook cost?

The formula for finding volume of a cone 1/3pi x r^2h. the volume of a cone is 300 cm^3 and the height of the cone is 10 what is the approximate radius of the cone

In may you used 400 kilowatt-hours of energy for electricity. a. calculate the total electrical energy use in joules. b. calculate your average power use in watts. c. assume that your power supplier generates electricity by burning oil. note that 1 liter of oil releases 12 million joules of energy. how much oil is needed to generate the electricity you use? give your answer in both liters and gallons. a. the total electrical energy use was nothing _ joules. (type an integer or a decimal.) b. the average power use is nothing _ watts. (round to the nearest whole number as needed.) c. to generate the electricity you used, nothing _ l is needed. (round to the nearest whole number as needed.) to generate the electricity you used, nothing _ gal is needed. (round to two decimal places as needed.)

There are four paths from the cabin to the lake. in how many ways can you walk from the cabin to the lake back?