40K decays to 40Ar with a half-life of 1.25 x 109 yr. Assume that rocks contain no 40Ar when they form, and that the only way 40Ar can be present is through the decay of 40K. If the ratio of 40K to 40Ar in a particular rock is found to be 1:7, what is the age of the rock

Cody started biking to the park traveling 15 mph, after some time the bike got a flat so cody walked the rest of the way, traveling 4 mph. if the total trip to the park took 6 hours and it was 46 miles away, how long did cody travel at each speed? solve using rate times time= distance

Tom can paint the fence in 12 hours, but if he works together with a friend they can finish the job in 8 hours. how long would it take for his friend to paint this fence alone?

Which statement shows that 6.24 is a rational number? a. 6.24 = 6.242424 b. 6.24 = 6.24 c. 6.24 = 68⁄33 d. 6.24 = 66⁄25