Perform each of the following operations using scientific nation.
(2.3 × 10³)(4.0 × 10^5)

(2.3 x 10^3)(4.0 x 10^5) =
2300 * 400000 = 920,000,000 or 9.2 x 10^8

or
(2.3 * 4.0)(10^3 * 10^5) =
9.2 * 10^8 = 920,000,000

He bought (a.) 4 packages of batteries. He returned the defective tape recorder for a store credit of $45 dollars. We know that he received $33 in refund, so the amount of money he spent on batteries is his store credit minus the refund ($45-$33), which is $12. Each package of batteries costs $3, so the amount of packages he bought can be found by dividing the money he spent by the cost per package, or $12/$3, which is equal to 4 packages.