8th Class Mathematics Linear Equations in One Variable Question Bank Linear equations in One Variable

  • question_answer
    Which of the following statements is INCORRECT?

    A)  Kusum buys some chocolates at the rate of Rs. 10 per chocolate. She also buys an equal number of candies at the rate of Rs. 5 per candy. She makes a 20% profit on chocolates and 8% profit on candies. At the end of the day, all chocolates and candies are sold out and her profit is Rs. 240. Therefore, Kusum buys 100 chocolates.

    B)  A carpenter charged Rs. 2500 for making a bed. The cost of materials used is Rs. 1100 and the labour charges are Rs. 200/hr. So, the carpenter will work for 7 hours.

    C)  On dividing Rs. 200 between A and B such that twice of A's share is less than 3 times B's share by 200. So, B's share is Rs. 120.

    D)  Madhulika thought of a number, double it and added 20 to it. On dividing the resulting number by 25, she gets 4. Hence, the required number is 45.

    Correct Answer: D

    Solution :

    [a] Let the number of chocolates purchased be x. \[\therefore \]The number of candies purchased \[=\text{ }x\] Cost of \[x\] chocolates \[=\text{Rs}\text{. }10x\] and cost of \[x\] candies \[=\text{ Rs}\text{. }5x\] According to question, 20% of 10x + 8% of \[5x=\text{Rs}.240\] \[\Rightarrow \frac{20}{100}\times 10x+\frac{8}{100}\times 5x=240\] \[\Rightarrow \frac{200x+40x}{100}=240\Rightarrow 240x=24000\] \[\Rightarrow x=\frac{24000}{240}\Rightarrow x=100\] Hence, the number of chocolates purchased is 100. [b] Let the carpenter worked for \[x\]hours. \[\therefore \] Labour charges for \[x\] hours \[=\text{ Rs}\text{. }200x\] According to question. \[200x+1100=2500\] \[\Rightarrow 200x=2500-1100\Rightarrow 200x=1400\] \[\Rightarrow x=\frac{1400}{200}\Rightarrow x=7\] Hence, the carpenter worked for 7 hours. [c] Let B's share be \[\text{Rs}\text{. }x\]. Since, \[2\text{ }\times \] A?s share \[=3\times \]B's share - 200 \[\Rightarrow A's\]share \[=\frac{3x-200}{2}\] According to question, \[\frac{3x-200}{2}+x=200\] \[\Rightarrow \frac{3x}{2}-\frac{200}{2}+x=200\Rightarrow \frac{3x}{2}-100+x=200\] \[\Rightarrow \frac{3x}{2}+x=200+100\Rightarrow \frac{3x+2x}{2}=300\] \[\Rightarrow \frac{5x}{2}=300\Rightarrow x=\frac{2x300}{5}\Rightarrow x=120\] Therefore, B's share \[\text{=Rs}\text{.}\,\,\text{120}\] [d] Let the number be \[x\]. Double the number and added 20 to it, we get 2x + 20 According to the question, \[\frac{1}{25}(2x+20)=4\] \[\Rightarrow 2x+20=4\times 25\Rightarrow 2x+2=100\] \[\Rightarrow 2x=100-20\to 2x=80\] \[\Rightarrow x=\frac{80}{2}\Rightarrow x=40\]


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