## Conversion Examples

1. How much gas money do you need to drive 300 miles, if your car gets 25 miles per gallon and a gallon of gas costs \$3.10?

Solution: ? \$ = 300 miles x (1 gallon/25 miles) x (3.10 \$/gallon) = \$37.20

2. Your display is 1280 pixels wide. How many 640-pixel images, when resized by scale factor S, can you display in a row?
Solution: ? img = 1280 px x (1 img/640 in-px) x (1 in-px/S px) = 2/S img

3. You're building a science instrument for a low earth orbiting satellite. To minimize power consumption, you want to run the processor at the lowest clock speed that still meets requirements. The instrument needs to take one measurement every meter of ground track; one measurement takes 50 instructions and the processor executes four instructions every two clock cycles. One orbit (40000 km) takes 90 minutes.

Solution: 92593 cycles/sec (92.6KHz).

4. How many gigabytes of storage do you need, worst case, to capture data from an 802.11g link (54Mbit/s) for one day?

Solution: ? GB = 54 Mbit/s x 24 hr x 3600 s/hr x MB/8 Mbit x GB/1024MB = 570GB