1. 

The mean temperature of Monday to Wednesday was 370 C and of Tuesday to Thursday was 340 C. what was the temperature on Thursday ?

I. The temperature on Thursday was 4/5th that of Monday.

II. The mean temperature of Monday and Thursday was 40.50 C .

III. The difference between the temperature on Monday and that on Thursday was 90 C.
A. I and II only
B. II and III only
C. I and III only
D. All I, II and III
E. None of these

Answer: Option C

Explanation:

M + T + W = (37 x 3)
M + T + W = 111 -------------- (i)

T + W + Th = (34 x 3)
T + W + Th = 102 ------------- (ii)

I gives, Th = 4/5 M M = 5/4 Th
Using it in (i), we get :
5/4 Th + T + W = 111 .............. (iii)

On subtracting (ii) from (iii),
we get : 1/4 Th = 9 Th = 36
Thus, I alone gives the answer.

II gives, M + Th = (40.5 x 2) M + Th = 81 .--------(iv)
On subtracting (ii) from (i), we get M - Th = 9 ----- (v)
From (iv) and (v), we get Th = 36.
Thus, II alone gives the answer.

III gives, M - Th = 9.
Clearly, III with given results, does not give the answer.
Correct answer is (C).