In a T20 cricket match, three players X, Y and Z scored a total of 37 runs. The ratio of number of runs scored by X to the number of runs scored by Y is equal to ratio of number of runs scored by Y to number of runs scored by Z. Value-I = Runs scored by X Value-II = Runs scored by Y Value-III = Runs scored by Z Which one of the following is correct ?
- (a) Value-I < Value-II < Value-III
- (b) Value-III < Value-II < Value-I
- (c) Value-I < Value-III < Value-II
- (d) Cannot be determined due to insufficient data ✓ UPSC's answer
Why the answer is (d)
• Let the runs scored by X, Y, and Z be $x$, $y$, and $z$ respectively.
• The condition 'ratio of X to Y is equal to ratio of Y to Z' implies $x/y = y/z$, which means $y^2 = xz$.
• This indicates that $x, y, z$ are in a Geometric Progression (GP).
• The total runs are given as $x + y + z = 37$.
• Since the common ratio $r$ of the GP is not specified, there are multiple integer solutions (e.g., if $r=1$, $x=y=z=12.33$ which is not integer, but if we consider non-integer or different integer sets like $1, 2, 4$ summing to 7, we can scale or find other integer triples).
• Specifically, for integer runs, we need $x, y, z$ to be integers in GP summing to 37. One possible set is $1, 2, 4$ (sum 7, not 37). Another is $4, 8, 16$ (sum 28). Let's check $1, 1, 1$ (sum 3). Actually, if $x, y, z$ are in GP, $y$ is the geometric mean. If $x=1, y=2, z=4$, sum=7. If we multiply by $k$, sum is $7k$. 37 is not divisible by 7. However, the GP doesn't have to be integers in the simplest form, but runs must be integers.
• Wait, if $x, y, z$ are integers in GP, they can be written as $a/r, a, ar$ or $a, ar, ar^2$. If $r$ is an integer, say $r=2$, terms are $a, 2a, 4a$. Sum $7a = 37$, no integer solution. If $r=1$, $3a=37$, no integer solution. If $r$ is a fraction, e.g., $1/2$, terms are $4a, 2a, a$, sum $7a=37$, no integer solution.
• Are there other GPs? $x, y, z$ integers. $y^2 = xz$. $x+z = 37-y$. $xz = y^2$. $x$ and $z$ are roots of $t^2 - (37-y)t + y^2 = 0$. Discriminant $D = (37-y)^2 - 4y^2 = 37^2 - 74y + y^2 - 4y^2 = 1369 - 74y - 3y^2$. For $x,z$ to be real, $D \ge 0$. For $x,z$ to be integers, $D$ must be a perfect square.
• Let's test values of $y$. If $y=12$, $D = 1369 - 888 - 432 = 49 = 7^2$. Roots: $(12 \pm 7)/2$? No, sum is $37-12=25$. Roots are $(25 \pm 7)/2 = 16, 9$. So $9, 12, 16$ is a valid integer GP ($12^2 = 144, 9 \times 16 = 144$). Here $x=9, y=12, z=16$ (Value-I < Value-II < Value-III) OR $x=16, y=12, z=9$ (Value-I > Value-II > Value-III).
• Since both increasing and decreasing GPs are possible with the same total, the order cannot be uniquely determined.
Why the other options are wrong
- (a) Value-I < Value-II < Value-III
- This option assumes the GP is increasing, but a decreasing GP (e.g., 16, 12, 9) is also a valid solution.
- (b) Value-III < Value-II < Value-I
- This option assumes the GP is decreasing, but an increasing GP (e.g., 9, 12, 16) is also a valid solution.
- (c) Value-I < Value-III < Value-II
- This option suggests an order that does not correspond to a standard Geometric Progression where the middle term is the geometric mean of the other two.
Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2025, held on 25 May 2025. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.