I have an SAT Question of the Day that I'm having trouble with. The question is: Seven cards in a pile are numbered 1 through 7. One card is drawn. The units digit of the sum of the numbers on the remaining cards is 7. What is the number on the drawn card?
The answer choices are:
1
3
5
6
7
The sum of 1+2+..+7 = 28
If after removing a card the unit digit of the sum of the remaining is 7, that sum could be either 27 or 17
For the 17, the card removed had to be a 10, not possible.
So the card removed was a 1
for the
i don't know bcuz im only n da 6th grade
To solve this SAT question, we need to find the number on the drawn card. The key piece of information is that the units digit of the sum of the numbers on the remaining cards is 7.
To make it easier, we can express the sum of the numbers on the remaining cards as an equation. Let's call the number on the drawn card "x."
The sum of the remaining cards is the sum of numbers from 1 to 7, minus the number on the drawn card:
1 + 2 + 3 + 4 + 5 + 6 + 7 - x
We know that the units digit of this sum is 7. The units digit is the rightmost digit. So, we need to find an x value that makes the units digit of the expression 1 + 2 + 3 + 4 + 5 + 6 + 7 - x equal to 7.
Let's calculate this sum:
1 + 2 + 3 + 4 + 5 + 6 + 7 = 28
To find the units digit of 28 - x equal to 7, we subtract 20 from 28 to get 8. Therefore, the units digit of 28 - x is the same as the units digit of x.
So, we need to find an x value where the units digit is 8. Looking at the answer choices:
1 does not have 8 as the units digit.
3 does not have 8 as the units digit.
5 does not have 8 as the units digit.
6 does not have 8 as the units digit.
However, 7 does have 8 as the units digit.
Therefore, the correct answer is 7.