Ex 2.5 Q2 Fractions and Decimals - NCERT Maths class 7

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Question

Express as rupees using decimals:

i) \(7\) paise ii) \(7\) rupees \(7\) paise iii) \(77\) rupees \(77\) paise
iv) \(50 \) paise v) \(235\) paise  

Text Solution

What is known?

Amount in paise.

What is unknown?

Amount in rupees.

Reasoning:

\(1\) paise \(=\) \(\begin{align}\frac{1}{{100}}\end{align}\)rupees

Steps:

i) \(7\) paise

\(100\) paise \(=\) \(1\) rupees

\(1\) paise \(=\) \( \begin{align}\frac{1}{{100}}\end{align}\) rupees

\(7\) paise \(=\) \(7\) \(×\)\(\begin{align}\frac{1}{{100}}\end{align}\)rupees \(=\) \(0.07\) rupees

ii) \(7\) rupees \(7\) paise

\(100\) paise \(=\) \(1\) rupees

\(1\) paise \(=\) \( \begin{align}\frac{1}{{100}}\end{align}\)rupees

\(7\) rupees \(7\) paise \(=\)  \(7\) rupees \(+\) \(7\) paise

\(=\) \(7\) rupees \(+\) \(7\) \(×\)\( \begin{align}\frac{1}{{100}}\end{align}\)rupees 

\(=\) \(7\) rupees \(+\) \(0.07\) rupees

\(=\) \(7.07\) rupees

iii) \(77\) rupees \(77\) paise

\(77\) rupees \(77\) paise \(=\)  \(77\) rupees \(+\) \(77\) paise

\(=\) \(77\) rupees + \(77\) \(×\) \(\begin{align}\frac{1}{{100}}\end{align}\)rupees

\(\because\)\(100\) paise \(=\) \(1\) rupees)

(\(\therefore\) \(1\) paise \(=\) \(\begin{align}\frac{1}{{100}}\end{align}\)rupees)

\(=\) \(77\) rupees \(+\) \(0.77\) rupees

\(=\) \(77.77\) rupees

iv) \(50\) paise

\(\therefore\) \(100\) paise \(=\) \(1\) rupees

\(\therefore\) \(1\) paise \(=\) \(\begin{align}\frac{1}{{100}}\end{align}\) rupees

\(50\) paise \(=\) \(50\) \(×\)\( \begin{align}\frac{1}{{100}}\end{align}\)rupees

=> \(50\) paise \(=\) \(\begin{align}\frac{{50}}{{100}}\end{align}\)rupees

\(50\) paise \(=\) \(0.50\) rupees

v) \(235\) paise

\(\therefore\) \(100\) paise \(=\) \(1\) rupees

\(\therefore\) \(1\) paise \(=\) \(\begin{align}\frac{1}{{100}}\end{align}\) rupees

\(235\) paise \(=\) \(235\) \(×\) \(\begin{align}\frac{1}{{100}}\end{align}\) rupees

\(235\) paise \(=\) \(\begin{align}\frac{{235}}{{100}}\end{align}\)rupees

\(235\)paise \(=\) \(2.35\) rupees