Question 1177669
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Represent walking one block west with W and one block south with S.<br>
From the bus stop to the store is 3 blocks west and 1 block south.  The number of different ways she can do that is the number of different ways of ordering the letters WWWS.  By a well-known counting principle, the number of ways she can do that is<br>
{{{4!/((3!)(1!)) = 4}}}<br>
From the store to her house is another 2 blocks west and another 3 blocks south of the store.  The number of ways she can make that part of the trip is the number of ways of ordering the letters WWSSS, which is<br>
{{{5!/((2!)(3!)) = 10}}}<br>
The fundamental counting principle then says the total number of ways she can stop at the store on the way from the bus stop to her house is 4*10 = 40.<br>
ANSWER: 40<br>