If the activity of a source is 70 Bq after 2 years, and 35 Bq after 15 years. How long will be until the activity is 8.75 Bq?

So if the half-life is two days, four half-lives is 8 days. Suppose a sample has a count rate of 3,200 Becquerel (Bq) at the start, then its count rate after 8 days would be 1/16th of 3,200 Bq = 200 Bq.

two charges are fixed in place on the x-axis as shown. the charge at x = 0 is negative and has magnitude q = 2 μcoulombs (1 μcoulomb = 10-6 coulombs). the charge at x = d, (d = +12 cm), is positive and has magnitude q = 4 μcoulombs. find a point x = xo along the x-axis at which the electric field is zero.

power out to power in less than 100%