12. Envelopes can be purchased for Rs 1.50 per pack of 100, Rs 1.00 per pack of 50, or Rs 0.03 each. What is the greatest number of envelopes that can be purchased for Rs 7.30?
Sol: 7.30 = 4*1.50 + 1*1.00 +10*0.03
Therefore, the greatest number of envelopes that can be purchased = 4*100+1*50+10*1= 460