91Ó°ÊÓ

Perform the calculations on a calculator. Two jets flew at \(938 \mathrm{km} / \mathrm{h}\) and \(1450 \mathrm{km} / \mathrm{h}\), respectively. How much faster was the second jet?

In Exercises \(57-68,\) perform the indicated operations. Is \(a^{-2}

Answer the given questions. Is subtraction associative? That is, in general, does \((a-b)-c\) equal \(a-(b-c) ?\) Explain.

Perform the indicated multiplications. A savings account of \(\$ 1000\) that earns \(r \%\) annual interest, compounded quarterly, has a value of \(1000(1+0.0025 r)^{2}\) after six months. Perform the indicated multiplication.

Is subtraction associative? That is, in general, does \((a-b)-c\) equal \(a-(b-c) ?\) Explain.

Perform the indicated operations. Is \(a^{-2}

Solve the given problems. Refer to Appendix \(B\) for units of measurement and their symbols. A baseball player's batting average (total number of hits divided by total number of at-bats) is expressed in decimal form from 0.000 (no hits for all at-bats) to 1.000 (one hit for each at-bat). A player's batting average is often shown as 0.000 before the first at-bat of the season. Is this a correct batting average? Explain.

In using aircraft radar, the expression \((2 R-X)^{2}-\left(R^{2}+X^{2}\right)\) arises. Simplify this expression.

Perform the calculations on a calculator. 1 MB of computer memory has 1,048,576 bytes. How many bytes are there in \(256 \mathrm{MB}\) of memory? (All numbers are exact.)

Perform the indicated operations. If \(a\) is a positive integer, simplify \(\left(x^{a} \cdot x^{-a}\right)^{5}\)