Helena invests a sum of money into an account that pays 6% compound interest per annum. Work out after how many years Helena will have trebled his investment. Give your answer as a whole number of years.

The axis of symmetry for the graph of the function f(x)=1/4^2+bx +10 is x=6. what is the value of b?

The number of nails of a given length is normally distributed with a mean length of 5.00 in, and a standard deviation of 0.03 in. find the number of nails in a bag of 120 that are less than 4.94 in. long.

Jada has a meal in a restaurant she adds up the prices listed on the menu for everything they ordered and gets a subtotal of $42.00. when the check comes, it says they also need to pay $3.99 in sales tax. what percentage of the subtotal is the sales tax