CAT 2025 Slot3 Quant: The sum of all the digits of the number
March 7, 2026 2026-03-07 15:16CAT 2025 Slot3 Quant: The sum of all the digits of the number
Split into $(10^{50}) + (10^{25} - 123)$.
$10^{25} - 123 = 99...99877$ (22 nines).
Number = $100...0099...99877$.
Sum = $1 + (22 \times 9) + 8 + 7 + 7 = 1 + 198 + 22 = \mathbf{221}$.
Detailed Step-by-Step Solution
Step 1: Analyze the second part $(10^{25} - 123)$
$10^{25}$ is 1 followed by 25 zeros. Subtracting 123:
$100,000...000 - 123 = 99,999...99877$.
Since we subtract from the $25^{th}$ power, the resulting number has 25 digits total.
The last three digits are $877$ (from $1000 - 123$). The remaining $25 - 3 = 22$ digits are all $9$s.
Step 2: Combine with $10^{50}$
$10^{50}$ is 1 followed by 50 zeros. The number $10^{25}-123$ will occupy the last 25 places of these zeros.
The number looks like:
$1 \underbrace{00...00}_{25 \text{ zeros}} \underbrace{99...99}_{22 \text{ nines}} 877$
Step 3: Calculate Sum of Digits
Sum $= 1 (\text{from } 10^{50}) + 0 (\text{zeros}) + (22 \times 9) + 8 + 7 + 7$
Sum $= 1 + 198 + 22$
Sum $= \mathbf{221}$.