Tammy had 900 red and blue buttons in a big box. 30% of them were blue buttons . She sold some of the blue buttons in the afternoon and the percentage of blue buttons dropped to 25% . How many blue buttons were left

X = number sold

.3(900) - x = .25(900-x)

Solve for x and subtract from 900.

To find out how many blue buttons were left, we need to calculate the total number of buttons and then subtract the number of red buttons remaining.

Step 1: Calculate the number of blue buttons initially.
Given that 30% of the buttons were blue, we can determine:
Blue buttons = 30% of 900 buttons
= (30/100) * 900
= 0.3 * 900
= 270 blue buttons initially.

Step 2: Calculate the total number of buttons remaining.
Since the blue buttons accounted for 25% after selling some, we can determine the total number of buttons using the equation:
Total buttons = 100% / 25% * blue buttons
= 4 * blue buttons
= 4 * 270
= 1080 buttons remaining.

Step 3: Calculate the number of red buttons remaining.
To determine the number of red buttons remaining, subtract the number of blue buttons remaining from the total number of buttons:
Red buttons remaining = Total buttons - Blue buttons remaining
= 1080 - 270
= 810 red buttons remaining.

Therefore, there were 810 blue buttons left.