If the radius is 3.5 what id the diameter

Can someone me out here number 4 plz

Agallon of apple juice cost $7 a pack of eight 4.23oz box of apple juice $2.39 which is a better deal

Suppose a laboratory has a 30 g sample of polonium-210. the half-life of polonium-210 is about 138 days how many half-lives of polonium-210 occur in 1104 days? how much polonium is in the sample 1104 days later? 9; 0.06 g 8; 0.12 g 8; 2,070 g