How many four-digit positive integers can be formed by using the digits from 1 to 9 so that two digits are equal to each other a
1 answer:
Answer:
432
Step-by-step explanation:
We are given that a four digit number can be formed by using digits from 1 to 9.
Two digits equal to each other and other two digits are equal to each other .
We have to find number of four digit numbers can be formed using digits from 1 to 9.
Total digits =9
Number of ways to filled first place =9
Number of ways to filled second place =1 because two digits are same
Number of ways to fill the third place =8 because different from previous two digits
Number of ways to fill the fourth place =1 because remaining two digits are same
Total number of ways to make four digit number =
Because two digits out of 4 and remaining two digits are same select out of 4
Total number of ways in which four digit number can be formed=
You might be interested in
Answer:
y=x, x-axis, y=x, y-axis
Explanation:
Reflecting the figure across three axes just moves it from one quadrant to another. It does not map the figure to itself.
Reflecting across the line y=x moves it from quadrant II to IV or vice-versa. If it is in quadrant I or III, it stays there. So the sequence of reflections x-axis (moves from I to IV), y=x (moves from IV to II), x-axis (moves from II to III), y=x (stays in III) will not map the figure to itself.
However, the last selection will map the figure to itself. The initial (and final) figure location, and the intermediate reflections are shown in the attached. The figure starts and ends as blue, is reflected across y=x to green, across x-axis to orange, across y=x to red, and finally across y-axis to blue again.
