Math worksheet with five questions on fractions, reciprocals, and number lines.
A math worksheet titled "QUESTION BANK" with five problems involving fractions, reciprocals, and number line representation.
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Step-by-step solution for: CBSE Class 8 Maths Rational Numbers Question bank
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Step-by-step solution for: CBSE Class 8 Maths Rational Numbers Question bank
Let's solve each question step by step from the Question Bank you provided.
---
$$
\left(\frac{9}{16} \times \frac{4}{12}\right) + \left(\frac{9}{16} \times \frac{-3}{9}\right)
$$
We can use the distributive property:
$$
a \times b + a \times c = a \times (b + c)
$$
Here, $ a = \frac{9}{16} $, $ b = \frac{4}{12} $, $ c = \frac{-3}{9} $
So,
$$
\frac{9}{16} \times \left( \frac{4}{12} + \frac{-3}{9} \right)
$$
Now simplify the terms inside the parentheses:
- $ \frac{4}{12} = \frac{1}{3} $
- $ \frac{-3}{9} = -\frac{1}{3} $
So:
$$
\frac{1}{3} + \left(-\frac{1}{3}\right) = 0
$$
Now:
$$
\frac{9}{16} \times 0 = 0
$$
✔ Answer: 0
---
$$
\frac{2}{5} \times \left( \frac{-3}{7} \right) - \frac{1}{6} \cdot \frac{3}{2} + \frac{1}{4} \times \frac{2}{5}
$$
Let’s simplify term by term.
#### First term:
$$
\frac{2}{5} \times \left( \frac{-3}{7} \right) = \frac{-6}{35}
$$
#### Second term:
$$
\frac{1}{6} \times \frac{3}{2} = \frac{3}{12} = \frac{1}{4}
$$
Note: The expression has a minus sign before this term, so:
$$
- \frac{1}{4}
$$
#### Third term:
$$
\frac{1}{4} \times \frac{2}{5} = \frac{2}{20} = \frac{1}{10}
$$
Now combine all:
$$
\frac{-6}{35} - \frac{1}{4} + \frac{1}{10}
$$
Find a common denominator. LCM of 35, 4, 10 is 140.
Convert each fraction:
- $ \frac{-6}{35} = \frac{-6 \times 4}{140} = \frac{-24}{140} $
- $ \frac{-1}{4} = \frac{-35}{140} $
- $ \frac{1}{10} = \frac{14}{140} $
Add:
$$
\frac{-24 - 35 + 14}{140} = \frac{-45}{140}
$$
Simplify:
$$
\frac{-45}{140} = \frac{-9}{28} \quad \text{(divided numerator and denominator by 5)}
$$
✔ Answer: $ \frac{-9}{28} $
---
#### a. The rational number that does not have a reciprocal.
> A rational number does not have a reciprocal if its reciprocal would involve division by zero.
The only rational number like this is 0, because $ \frac{1}{0} $ is undefined.
✔ Answer: 0
#### b. The rational numbers that are equal to their reciprocals.
Let $ x = \frac{1}{x} $
Then:
$$
x^2 = 1 \Rightarrow x = \pm 1
$$
Check:
- $ 1 \times 1 = 1 $ → reciprocal is 1 ✔
- $ -1 \times -1 = 1 $ → reciprocal is -1 ✔
✔ Answer: 1 and -1
#### c. The rational number that is equal to its negative.
Let $ x = -x $
Then:
$$
2x = 0 \Rightarrow x = 0
$$
✔ Answer: 0
---
#### a. Zero has ________ reciprocal.
Zero has no reciprocal.
✔ Answer: no
#### b. The reciprocal of $-5$ is ________.
Reciprocal of $-5$ is $ \frac{1}{-5} = -\frac{1}{5} $
✔ Answer: $-\frac{1}{5}$
#### c. The reciprocal of $ \frac{1}{x} $, where $ x \neq 0 $, is ________.
Reciprocal of $ \frac{1}{x} $ is $ x $
✔ Answer: $ x $
#### d. The product of two rational numbers is always a ________.
Product of two rational numbers is always a rational number.
✔ Answer: rational number
#### e. The reciprocal of a positive rational number is __________.
A positive rational number has a positive reciprocal.
Example: $ \frac{2}{3} $ → reciprocal $ \frac{3}{2} $ → positive
✔ Answer: positive rational number
---
#### a. $ \frac{7}{4} $
This is $ 1.75 $, which lies between 1 and 2, closer to 2.
On the number line:
- Mark 1 and 2.
- Divide into 4 parts: $ \frac{1}{4}, \frac{2}{4}, \frac{3}{4}, \frac{4}{4}=1 $
- $ \frac{7}{4} = 1 + \frac{3}{4} $ → So go 3/4 beyond 1.
✔ Place a point at 1.75
#### b. $ \frac{-5}{6} $
This is approximately $ -0.833 $, between -1 and 0, closer to -1.
On the number line:
- Mark -1 and 0.
- Divide into 6 parts: $ -\frac{1}{6}, -\frac{2}{6}, ..., -\frac{5}{6} $
- $ \frac{-5}{6} $ is just $ \frac{1}{6} $ short of -1.
✔ Place a point at about -0.833
---
1. 0
2. $ \frac{-9}{28} $
3.
a. 0
b. 1 and -1
c. 0
4.
a. no
b. $ -\frac{1}{5} $
c. $ x $
d. rational number
e. positive rational number
5.
a. $ \frac{7}{4} = 1.75 $ → mark between 1 and 2
b. $ \frac{-5}{6} \approx -0.833 $ → mark between -1 and 0
Let me know if you'd like a visual sketch of the number line!
---
1. Find using distributivity:
$$
\left(\frac{9}{16} \times \frac{4}{12}\right) + \left(\frac{9}{16} \times \frac{-3}{9}\right)
$$
We can use the distributive property:
$$
a \times b + a \times c = a \times (b + c)
$$
Here, $ a = \frac{9}{16} $, $ b = \frac{4}{12} $, $ c = \frac{-3}{9} $
So,
$$
\frac{9}{16} \times \left( \frac{4}{12} + \frac{-3}{9} \right)
$$
Now simplify the terms inside the parentheses:
- $ \frac{4}{12} = \frac{1}{3} $
- $ \frac{-3}{9} = -\frac{1}{3} $
So:
$$
\frac{1}{3} + \left(-\frac{1}{3}\right) = 0
$$
Now:
$$
\frac{9}{16} \times 0 = 0
$$
✔ Answer: 0
---
2. Using appropriate properties, find:
$$
\frac{2}{5} \times \left( \frac{-3}{7} \right) - \frac{1}{6} \cdot \frac{3}{2} + \frac{1}{4} \times \frac{2}{5}
$$
Let’s simplify term by term.
#### First term:
$$
\frac{2}{5} \times \left( \frac{-3}{7} \right) = \frac{-6}{35}
$$
#### Second term:
$$
\frac{1}{6} \times \frac{3}{2} = \frac{3}{12} = \frac{1}{4}
$$
Note: The expression has a minus sign before this term, so:
$$
- \frac{1}{4}
$$
#### Third term:
$$
\frac{1}{4} \times \frac{2}{5} = \frac{2}{20} = \frac{1}{10}
$$
Now combine all:
$$
\frac{-6}{35} - \frac{1}{4} + \frac{1}{10}
$$
Find a common denominator. LCM of 35, 4, 10 is 140.
Convert each fraction:
- $ \frac{-6}{35} = \frac{-6 \times 4}{140} = \frac{-24}{140} $
- $ \frac{-1}{4} = \frac{-35}{140} $
- $ \frac{1}{10} = \frac{14}{140} $
Add:
$$
\frac{-24 - 35 + 14}{140} = \frac{-45}{140}
$$
Simplify:
$$
\frac{-45}{140} = \frac{-9}{28} \quad \text{(divided numerator and denominator by 5)}
$$
✔ Answer: $ \frac{-9}{28} $
---
3. Write:
#### a. The rational number that does not have a reciprocal.
> A rational number does not have a reciprocal if its reciprocal would involve division by zero.
The only rational number like this is 0, because $ \frac{1}{0} $ is undefined.
✔ Answer: 0
#### b. The rational numbers that are equal to their reciprocals.
Let $ x = \frac{1}{x} $
Then:
$$
x^2 = 1 \Rightarrow x = \pm 1
$$
Check:
- $ 1 \times 1 = 1 $ → reciprocal is 1 ✔
- $ -1 \times -1 = 1 $ → reciprocal is -1 ✔
✔ Answer: 1 and -1
#### c. The rational number that is equal to its negative.
Let $ x = -x $
Then:
$$
2x = 0 \Rightarrow x = 0
$$
✔ Answer: 0
---
4. Fill in the blanks:
#### a. Zero has ________ reciprocal.
Zero has no reciprocal.
✔ Answer: no
#### b. The reciprocal of $-5$ is ________.
Reciprocal of $-5$ is $ \frac{1}{-5} = -\frac{1}{5} $
✔ Answer: $-\frac{1}{5}$
#### c. The reciprocal of $ \frac{1}{x} $, where $ x \neq 0 $, is ________.
Reciprocal of $ \frac{1}{x} $ is $ x $
✔ Answer: $ x $
#### d. The product of two rational numbers is always a ________.
Product of two rational numbers is always a rational number.
✔ Answer: rational number
#### e. The reciprocal of a positive rational number is __________.
A positive rational number has a positive reciprocal.
Example: $ \frac{2}{3} $ → reciprocal $ \frac{3}{2} $ → positive
✔ Answer: positive rational number
---
5. Represent these numbers on the number line:
#### a. $ \frac{7}{4} $
This is $ 1.75 $, which lies between 1 and 2, closer to 2.
On the number line:
- Mark 1 and 2.
- Divide into 4 parts: $ \frac{1}{4}, \frac{2}{4}, \frac{3}{4}, \frac{4}{4}=1 $
- $ \frac{7}{4} = 1 + \frac{3}{4} $ → So go 3/4 beyond 1.
✔ Place a point at 1.75
#### b. $ \frac{-5}{6} $
This is approximately $ -0.833 $, between -1 and 0, closer to -1.
On the number line:
- Mark -1 and 0.
- Divide into 6 parts: $ -\frac{1}{6}, -\frac{2}{6}, ..., -\frac{5}{6} $
- $ \frac{-5}{6} $ is just $ \frac{1}{6} $ short of -1.
✔ Place a point at about -0.833
---
✔ Final Answers Summary:
1. 0
2. $ \frac{-9}{28} $
3.
a. 0
b. 1 and -1
c. 0
4.
a. no
b. $ -\frac{1}{5} $
c. $ x $
d. rational number
e. positive rational number
5.
a. $ \frac{7}{4} = 1.75 $ → mark between 1 and 2
b. $ \frac{-5}{6} \approx -0.833 $ → mark between -1 and 0
Let me know if you'd like a visual sketch of the number line!
Parent Tip: Review the logic above to help your child master the concept of rational numbers worksheet 8th grade.