# Chapter 13 - Counting and Probability - 13.3 Probability - 13.3 Asses Your Understanding - Page 866: 63

$0.3$

#### Work Step by Step

We know that $\text{probability}=\frac{\text{number of favourable outcomes}}{\text{number of all outcomes}}=\frac{n(E)}{n(S)}.$ Hence here because we have $n(E)=20+10=30$ houses with at least $30000\$$income, in total we have$n(S)=100$houses, therefore$\text{probability}=\frac{30}{100}=0.3.\$

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