Question

the symbol of an unprefixed scientific unit has been left off of each measurement in the table below. fill in the missing unit symbols.
note: by \scientific\ unit we mean the si unit, or unit approved for use with the si, that is most often used by chemists for each measurement.

the length of a car = 5. □
the world record for the 100m freestyle swim = 44.9 □
the length of a pencil = 0.15 □
the mass of a newborn baby = 3000. □

Explanation:

Step1: Length of a car

A typical car length is around a few meters. So the unit for 5. should be meters (m).

Step2: Length of a pencil

A pencil is about 15 centimeters, and 1 meter = 100 centimeters, so 0.15 meters is 15 centimeters. So the unit for 0.15 should be meters (m) or more appropriately, since 0.15 meters is 15 cm, but in SI units, meters is base, but also, 0.15 meters can be thought of as 15 centimeters, but the unit here, considering the number, 0.15 meters is 15 cm, so the unit is meters (m), or maybe decimeters? Wait, no, 0.15 meters is 15 cm, which is a common pencil length. Wait, 0.15 meters is 15 centimeters, so the unit is meters (m). Alternatively, 0.15 meters is 1.5 decimeters, but the standard unit for length here would be meters, but maybe centimeters? Wait, 0.15 meters is 15 cm, so if the number is 0.15, the unit is meters (m). Wait, no, 15 cm is 0.15 m, so the unit is meters (m).

Step3: 100m freestyle swim time

Swim times for 100m freestyle are in seconds. So 44.9 seconds is a reasonable time, so the unit is seconds (s).

Step4: Mass of a newborn baby

A newborn baby's mass is around 3 - 4 kilograms, which is 3000 - 4000 grams. So 3000 grams is 3 kilograms, so the unit is grams (g).

Answer:

• the length of a car = 5. $\boldsymbol{m}$ (meters)
• the length of a pencil = 0.15 $\boldsymbol{m}$ (meters) or 0.15 $\boldsymbol{dm}$ (decimeters) but more likely meters (since 0.15 m = 15 cm, a common pencil length)
• the world record for the 100m freestyle swim = 44.9 $\boldsymbol{s}$ (seconds)
• the mass of a newborn baby = 3000 $\boldsymbol{g}$ (grams)

(Note: For the pencil, if we consider 0.15 meters is 15 cm, which is correct, so unit is meters (m). Alternatively, if we use centimeters, 15 cm, but the number is 0.15, so unit is meters. For the car, 5 meters is reasonable. For the swim, seconds. For the baby, grams (3000 grams = 3 kg, which is a typical newborn mass).)