Exercise: 5-F
Mental Maths
Q1: Fill in the blanks:
i. 6 hundredths in decimal form is _______.
Step:
\[
6\text{ hundredths} = \frac{6}{100} = 0.06
\]
Answer: 0.06
ii. \(\frac{6}{25}\) in decimal form is _______.
Step:
\[
\frac{6}{25} = \frac{24}{100} = 0.24
\]
Answer: 0.24
iii. 2 m 15 cm + 6 m 5 cm = _______ metres.
Step:
Convert cm to metres:
\[
15\text{ cm} = 0.15\text{ m},\quad 5\text{ cm} = 0.05\text{ m}
\]
Add:
\[
(2 + 0.15) + (6 + 0.05) = 2.15 + 6.05 = 8.20\text{ m}
\]
Answer: 8.20 metres
iv. 15P + 5P = ₹ ________.
Step:
\[
15P + 5P = 20P = \frac{20}{100} = ₹0.20
\]
Answer: ₹0.20
v. 15 km + 75 m = _______.
Step:
Convert 75 m to km:
\[
75\text{ m} = \frac{75}{1000} = 0.075\text{ km}
\]
Add:
\[
15 + 0.075 = 15.075\text{ km}
\]
Answer: 15.075 km
vi. (2 cm – 5 mm) = _______ cm.
Step:
Convert 5 mm to cm:
\[
5\text{ mm} = \frac{5}{10} = 0.5\text{ cm}
\]
Subtract:
\[
2 – 0.5 = 1.5\text{ cm}
\]
Answer: 1.5 cm
Q2: Write (T) for true and (F) for false for each of the statements given below:
i. 3 m 5 cm = 3.5 m
Step:
5 cm = 0.05 m
\[
3 + 0.05 = 3.05 \ne 3.5
\]
Answer: False (F)
ii. 16 km 30 m = 16.30 km
Step:
30 m = 0.030 km
\[
16 + 0.030 = 16.030 \ne 16.30
\]
Answer: False (F)
iii. ₹8 + 6P = ₹(8.60)
Step:
6 paise = ₹0.06
\[
₹8 + ₹0.06 = ₹8.06 \ne ₹8.60
\]
Answer: False (F)
iv. 0.03 = 3 hundredths
Step:
\[
\frac{3}{100} = 0.03
\]
Answer: True (T)
v. 7 kg 80 g = 7.8 kg
Step:
80 g = 0.08 kg
\[
7 + 0.08 = 7.08 \ne 7.8
\]
Answer: False (F)
vi. 0.1 + 0.01 + 0.001 = 0.111
Step:
0.100 + 0.010 + 0.001 ------- 0.111
Answer: True (T)
Leave a Comment