What number has the same value as 30 tens

What is the number 321,000,000 in scientific notation? also what is the number? ?

What is the volume of a cone with a height of 6 cm in the radius of 2 cm

Aproduction manager test 10 toothbrushes and finds that their mean lifetime is 450 hours. she then design sales package of this type of toothbrush. it states that the customers can expect the toothbrush to last approximately 460 hours. this is an example of what phase of inferential statistics