Question:medium
If \( {}^9P_3 + 5 \cdot {}^9P_4 = {}^{10}P_r \), then the value of \( 'r' \) is:
If \( {}^9P_3 + 5 \cdot {}^9P_4 = {}^{10}P_r \), then the value of \( 'r' \) is:
Show Hint
Double-check the formulas and properties of permutations carefully. Ensure the values of \( n \) and \( r \) are correctly substituted.
Updated On: Nov 28, 2025
- \( 4 \)
- \( 8 \)
- \( 5 \)
- \( 7 \)
Top Questions on permutations and combinations
- The value of the expression \( {}^{47} C_4 + \sum_{j=1}^{5} {}^{52-j} C_3 \) is:
- WBJEE - 2025
- Mathematics
- permutations and combinations
- There are 6 boys and 4 girls. Arrange their seating arrangement on a round table such that 2 boys and 1 girl can't sit together.
- MHT CET - 2025
- Mathematics
- permutations and combinations
- How many different 4-letter words can be formed from the letters of the word "BINARY" without repetition?
- BITSAT - 2025
- Mathematics
- permutations and combinations
- Want to practice more? Try solving extra ecology questions todayView All Questions