What is the mantissa of the common log of the number?

Correct answer: c 0.3701

log 0.002345 = −2.62986 = −3 + 0.37014, so the mantissa is .3701.

Why the other options are wrong

• a 0.6289: The digits are swapped (0.6289 for 0.6298); in fact −2.62986 = −3 + 0.37014 gives the mantissa .3701.
• b 0.002345: This is the number itself; the mantissa is the decimal part of the log.
• d 0.6298: 0.6298 is the decimal part of −2.62986, but to keep the mantissa positive we write −3 + 0.37014, so it is .3701.