Chapter 4 - Probability - 4-6 Counting - Beyond the Basics - Page 184: 39

$12$

We have 3 coins that are worth less than 0.25: 0.01, 0.05 and 0.10. Therefore the possibilities: $2×0.10+0.05$ $2×0.10+5×0.01$ $0.10+3×0.05$ $0.10+2×0.05+5×0.01$ $0.10+1×0.05+10×0.01$ $0.10+15×0.01$ $5×0.05$ $4×0.05+5×0.01$ $3×0.05+10×0.01$ $2×0.05+15×0.01$ $1×0.05+20×0.01$ $25×0.01$ Therefore there are 12 possibilities.