Math CentralQuandaries & Queries


Question from Jora, a student:

Electronic Store

John opened an electronic store in December. During his first month, he sold 10 LCD TVs and 20 Plasma TVs. His income during that month was $12800. In January, he sold 25 LCD TVs and 40 Plasma TVs for an income of $27600. In February he projects to sell 30 LCD TVs and 50 Plasma TVs. If John expenses are $28900 in February, how much money will he have after paying the expenses?

Hi Jora,

Suppose that an LCD TV sells for L dollars and a Plasma TV sells for P dollars. In December John's income was then

\[10 L + 20 P = 12800 \mbox{ dollars}\]

Write the equation for his income in in January. Solve the equations for L and P. What is John's expected income in February? After paying his expenses in February how much id he make in February?



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