The average height of 13 girls in a class is $144 \frac{8}{13}$ cm. The average height of 11 boys in the class is $169 \frac{5}{11}$ cm. There are only 24 students in the class. What is the overall average height (in cm) of all the students together in the class?

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The average height of the students in a class of 10 is 105 cm. If 20 more students with an average height of 120 cm join the class, what will the new average height be?

The correct option is D 115 cmTotal height of 10 students =10×105=1050cmTotal height of 20 students =20×120=2400cm∴ total height of 30 students =1050+2400=3450Hence average height of 30 students =345030=115cm

The average height of the students in a class of $10$ is $105$ cm. If $20$ more students with an average height of $120$ cm join the class, what will the new average height be?

The correct option is D $115$ cm
Total height of $10$ students $= 10 \times 105 = 1050 c m$
Total height of $20$ students $= 20 \times 120 = 2400 c m$
$∴$ total height of $30$ students $= 1050 + 2400 = 3450$
Hence average height of $30$ students $= \frac{3450}{30} = 115 c m$