We want possible values of:
E − S
There are:
• 10 numbers with even tenths digit → rounded up
• 20 numbers with odd tenths digit → rounded down
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Step 1: Error from each type
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Even tenths digit → rounded UP
Possible tenths digits:
0.0, 0.2, 0.4, 0.6, 0.8
But numbers are NOT integers, so decimal part cannot be 0.0.
Rounding-up errors:
.2 → +0.8
.4 → +0.6
.6 → +0.4
.8 → +0.2
So each even-tenths number contributes:
+0.2, +0.4, +0.6, or +0.8
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Odd tenths digit → rounded DOWN
Possible decimal parts:
.1, .3, .5, .7, .9
Errors:
-0.1, -0.3, -0.5, -0.7, -0.9
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Step 2: Important observation
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Every contribution is a multiple of 0.1.
So total (E − S) must also be a multiple of 0.1.
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Step 3: Find the range
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Largest possible value:
10(0.8) + 20(-0.1)
= 8 - 2
= 6
And this IS achievable exactly:
• all even tenths digits are .2
• all odd tenths digits are .1
Example:
10 numbers like 3.2 → each contributes +0.8
20 numbers like 5.1 → each contributes -0.1
Total:
10(0.8) + 20(-0.1) = 6
So II is possible.
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Smallest possible value:
10(0.2) + 20(-0.9)
= 2 - 18
= -16
Also achievable exactly:
• even tenths digits all .8
• odd tenths digits all .9
So I is possible.
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Step 4: Can 10 happen?
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No, because the maximum possible value is 6.
So III is impossible.
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Final Answer
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I ✔
II ✔
III ✘
Answer = B