Which prefix has the multiplier 0.0001?

• A. femto- f
• B. nano- n
• C. micro- µ
• D. milli- m

Answer: (D)

The idea being tested is how metric prefixes translate to powers of ten. Each prefix corresponds to a specific multiplier: femto- is 10^-15, nano- is 10^-9, micro- is 10^-6, and milli- is 10^-3. The quantity 0.0001 can be written as 1 × 10^-4. That exponent (−4) isn’t matched by any of the prefixes listed here, so there isn’t a standard prefix that has exactly that multiplier.

A helpful way to see this is to relate the prefixes to the actual scale: 0.001 m is one milli of a meter, 0.000001 m is one micro of a meter, and so on. If you want to express 0.0001 m using prefixes, you’d still use a prefix for a portion of the unit (like micro), but you’d need a coefficient (for example, 100 micro-meters equals 0.0001 meters). The key takeaway is that 0.0001 is 10^-4, which isn’t the exact multiplier of the standard prefixes shown.