How many two-letter words can be formed using letters from the word SPACE, when repetition of letters is allowed?
Two-letter word is to be formed out of the letters of the word SPACE.
When repetition of the letters is allowed
1st letter can be selected in 5 ways
2nd letter can be selected in 5 ways
∴ By using the fundamental principle of multiplication, the total number of 2-letter words = 5 × 5 = 25