Isotope of an element differ in their

The ansewer is Atomic masses

Isotopes of an element have a same atomic number but differ in their atomic masses. Atomic number indicates a number of protons and atomic mass indicate the number of neutrons plus proton present in the atom. So atoms with the same number of protons but different number of neutrons are termed as isotopes.

9.9 years

a = p(1 + rt) . . account balance after time t at rate r starting with principal p

3000 = 2500(1 + 0.0202t) . . filling in the given numbers

1.2 = 1 + 0.0202t . . divide by 2500

0.2 = 0.0202t . . . subtract 1

0.2/0.0202 = t ≈ 9.901

it will take about 9.9 years for the account balance to reach $3000.

he is very short, and he can only reach halfway up on the elevator buttons. but on a rainy day, he has his umbrella with him, and he uses it to poke the button at the top.