A, B, and C jointly bought a batch of exercise books with a total of 27 yuan, and each contributed the same amount. Since A wants 15 fewer copies than C, and B and C want the same amount, each of B and C should give A 1.5 yuan. How many copies did the three of them buy together?
甲、乙、丙三人共出27元合伙买了一批练习本，每人出资相同．由于甲比丙少要15本，乙和丙要的一样多，因此乙和丙每人都要给甲1.5元．三人合伙买了多少本？
<gadget id="calculator">2 / 15</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">1.5 * (2/15)</gadget>
<output>0.2</output>

<gadget id="calculator">27 / 0.2</gadget>
<output>135</output>

<result>135</result>