#### Question: Why can a pace or a footstep not be used as a standard unit of length?

**Answer: **The size of the foot varies from person to person. If footsteps of two persons are used to measure the length respectively, then the two distances may not be equal. Thus, a footstep is not a constant quantity. Hence, it cannot be used as a standard unit of length.

#### Question: Arrange the following lengths in their increasing magnitude:

1 metre, 1 centimetre, 1 kilometre, 1 millimetre

**Answer: **1 cm = 10 mm

1 m = 100 cm = 1000 mm

Again, 1 km = 1000 m = 100000 cm = 10000000 mm.

Hence, 1 mm is smaller than 1 cm, 1 cm is smaller than 1 m, and 1 m is smaller than 1 km, i.e.,

**1 millimetre < 1 centimetre < 1 metre < 1 kilometre**

#### Question: The height of a person is 1.65 m. Express this in cm and mm.

**Answer: **Height of the person = 1.65 m

1 m = 100 cm

1.65 m = 100 × 1.65 = 165 cm

Hence, the height of the person is 165 cm.

Again, 1 m = 100 cm = 1000 mm

Therefore, 1.65 m = 1.65 × 10 = 1650 mm

Hence, the height of the person is 1650 mm.

#### Question: The distance between Radha’s home and her school is 3250 m. Express this distance in km.

**Answer: **The distance between Radha’s home and her school is 3250 m.

1 km = 1000 m

i.e., 1000 m = 1 km

3250 = 1/1000× 3250 = 3.25 km.

#### Question: List the common characteristics of living things.

**Answer: **Some common characteristics of living things are that they

- require food
- respire and excrete waste material
- respond to stimuli in their environment
- reproduce to maintain their number
- move from one place to another
- grow and die