Helium atoms have 2 electrons both have a -1 charge. Every proton has a +1 charge. If the helium atom has no charge, how many protons must it have?

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 $740 is invested at an interest rate of 11% per year and is compounded continuously, how much will the investment be worth in 7 years? use the continuous compound interest formula a = pert.

:24% of students in a class are girls. if there are less than 30 students in this class, how many students are there? how many girls are there?