the average temperature of june july and august was 31 degrees the average temperature of july august and september was 28 degrees if the temperature of june was 30 degrees find the temperature of september in degrees a)22 b) 19 c)20 d)21; the average temperature of june july and august was 31 degrees the average temperature of july august and september was 28 degrees if the temperature of june was 30 degrees find the temperature of september in degrees a)22 b) 19 c)20 d)21
Answers
Hello there!
Average means the sum of observations divided by the number of observations.
In the first part, the average of the observed temperatures of Jun, Jul and Aug is 31°. If you multiply this with 3 (which is the number of months), then you get 93 as the Sum.
⇒ Jun + Jul + Aug = 93
In the second part, the average of the observed temperatures of Jul, Aug, and Sep is 28°. If you multiply this with 3 (which is the number of months), then you get 84 as the Sum.
⇒ Jul + Aug + Sep = 84
They also mentioned that June's temperature was 30°. Subtract this value from the first equation:
⇒ Jun + Jul + Aug - Jun = 93 - Jun
⇒ Jul + Aug = 93 - 30 = 63
Now you know the sum of Jul and Aug alone. If you see the equation of the second case, you can put this Jul + Aug value inside the second case's equation!!!
⇒ (Jul + Aug) + Sep = 84
⇒ 63 + Sep = 84
⇒ ∴ Sep = 84 - 63 = 21 degrees
So, Option D ⇒ 21 is the correct answer. That's it!