The average temperature was 37C for Monday to Wednesday and 34C for Tuesday to Thursday . If the temperature on Thursday was 4/5 th of that of Monday,what was the temperature on Thursday?

One Answer on this Question

1. First write equations from info:
   (A) (Mon + Tue + Wed)/3 = 111 Rearrange as ——–> Tue + Wed = 111 – Mon
   (B) (Tue + Wed + Thu)/3 =102 Rearrange as ——–> Tue + Wed = 102 – Thu
   (C) Thu = 0.8(Mon)

   Substitute equation C into B:
   (B) Tue + Wed = 102 – 0.8(Mon)

   At this point I changed the values for clearer algebra:
   Mon = x
   Tue + Wed = y

   Re-write equations A & B with new values:
   (A) y = 111 – x
   (B) y = 102 – 0.8x

   Solve simultaneous equations:

   111 – x = 102 – 0.8x
   111 – 102 = x – 0.8x (Re-arraged)
   9 = 0.2x
   x = 45

   Thus, Mon = 45C

   Thu = 0.8(45)
   Thu = 36C

   So the answer is it was 36C on Thursday

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