nutley public schools

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156 123
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Let \( d \) be the distance between City A and City B.
Time from A to B = \( \frac{d}{80} \)
Time from B to A = \( \frac{d}{100} \)
Total time = \( \frac{d}{80} + \frac{d}{100} = 9 \)
Finding a common denominator:
\( \frac{5d + 4d}{400} = 9 \)
\( \frac{9d}{400} = 9 \)
\( 9d = 3600 \)
\( d = 400 \)
#### 400 kilometers