Please help will reward correct answer brain list Which number is not in scientific notation?

6 ⋅ 1025

2.01 ⋅ 10−2

1.3 ⋅ 10−4

0.5 ⋅ 103

Determine whether the set of whole numbers is closed under addition. explain why the set is or is not closed. give an example.

Cassie is traveling 675 miles today to visit her brother and his family. so far, she has stopped for gas three times. at the first stop, she put in 7.1 gallons of gas and paid $23.79. at her second stop, she put in 5.8 gallons of gas and paid $19.08. and, at the third stop, 6.6 gallons and paid $20.39. at which stop did casey pay the most for gas?

If np3 /nc2 = 6, find the value of n