Answer:
[tex]\qquad\qquad\qquad\boxed{ \sf{ \: \bf \:Loss\% \: = \: 16 \: \% \: }} \\ \\ [/tex]
Step-by-step explanation:
Given that, By selling 21 apples, vendor losses the selling price of 4 apples.
Let assume that
[tex]\sf \:Selling \: Price \: of \: 1 \: apple \: = \: Rs \: x \\ \\ [/tex]
So,
[tex]\sf\implies \sf \:Selling \: Price \: of \: 21 \: apples \: = \: Rs \: 21x \\ \\ [/tex]
Now,
[tex] \sf \:Loss = Selling \: Price \: of \: 4 \: apples \: \\ \\ [/tex]
[tex]\sf\implies \sf \:Loss = Rs \: 4x \: \\ \\ [/tex]
We know,
Selling Price, Cost Price and Loss are connected by the symbol
[tex]\sf \:Cost \: Price \: = \: Selling \: Price \: + \: Loss \\ \\ [/tex]
On substituting the values, we get
[tex]\sf \:Cost \: Price \: = \: 21x \: + \: 4x \\ \\ [/tex]
[tex]\sf\implies \sf \:Cost \: Price \: = \: 25x \\ \\ [/tex]
Now, We know
Selling Price, Cost Price and Loss % are connected by the relationship
[tex]\sf \:Loss\% \: = \: \dfrac{Loss}{Cost \: Price} \times 100 \: \% \\ \\ [/tex]
[tex]\sf \:Loss\% \: = \: \dfrac{4x}{25x} \times 100 \: \% \\ \\ [/tex]
[tex]\sf \:Loss\% \: = \: \dfrac{4}{1} \times 4 \: \% \\ \\ [/tex]
[tex]\sf\implies \bf \:Loss\% \: = \: 16 \: \% \\ \\ [/tex]
[tex]\rule{190pt}{2pt}[/tex]
Additional Information
[tex]\begin{gathered}\: \: \: \: \: \: \begin{gathered}\begin{gathered} \footnotesize{\boxed{ \begin{array}{cc} \small\underline{\frak{\pmb{ {More \: Formulae}}}} \\ \\ \bigstar \: \bf{Gain = \sf S.P. \: – \: C.P.} \\ \\ \bigstar \:\bf{Loss = \sf C.P. \: – \: S.P.} \\ \\ \bigstar \: \bf{Gain \: \% = \sf \Bigg( \dfrac{Gain}{C.P.} \times 100 \Bigg)\%} \\ \\ \bigstar \: \bf{Loss \: \% = \sf \Bigg( \dfrac{Loss}{C.P.} \times 100 \Bigg )\%} \\ \\ \\ \bigstar \: \bf{S.P. = \sf\dfrac{(100+Gain\%) or(100-Loss\%)}{100} \times C.P.} \\ \: \end{array} }}\end{gathered}\end{gathered}\end{gathered}[/tex]