A pencil costs $3 and a pen costs $7. If pens and pencils have to be bought independently and in lots
which are multiples of 5. Are the number of pens bought equal to the number of pencils bought.
1)Total money spend was $100.
2)Total money spend was $ 200.
Let the no of pencils bought = 5x and no of pens = 5y
The question asks is x=y?
From F.S 1, we know that \(3*5x+7*5y = 100\)
or 3x+7y = 20. The only solution for this equation with positive integrals values for (x,y) is \(x=y=2\). Sufficient.
From F.S. 2, we know that\(3x+7y = 40\). Now, \(y=1,x=11\) satisfies this equation. Also, \(y=4,x=4\) satisfies the equations. Insufficient.
Though not a good question for GMAT.
All that is equal and not-Deep Dive In-equality
Hit and Trial for Integral Solutions