Rohans purchase

The cost of a pen is ₹ 15 ¾ and a pencil for ₹ 4 ¼. If Rohan purchased 3 pens and 12 pencils, which items cost him more and by how much?

Correct answer:

x = pencils
d =  3 ³⁄₄ = 15/4

Step-by-step explanation:

$$\begin{gathered} a=15\frac{3}{4}=15+\frac{3}{4}=\frac{15\cdot 4+3}{4}=\frac{60+3}{4}=\frac{63}{4}=15\frac{3}{4}=15.75 \\ b=4\frac{1}{4}=4+\frac{1}{4}=\frac{4\cdot 4+1}{4}=\frac{16+1}{4}=\frac{17}{4}=4\frac{1}{4}=4.25 \\ A=3\cdot a=3\cdot \frac{63}{4}=\frac{3\cdot 63}{4}=\frac{189}{4}=47.25 \\ B=12\cdot b=12\cdot \frac{17}{4}=\frac{12\cdot 17}{4}=\frac{204}{4}=51 \\ B>A \\ x=pencils \end{gathered}$$

$d=B-A=51-\frac{189}{4}=\frac{51\cdot 4}{4}-\frac{189}{4}=\frac{204}{4}-\frac{189}{4}=\frac{204-189}{4}=\frac{15}{4}=3\frac{3}{4}=3.75$

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