You have to be very careful how you set this up. For every girl (who counts as 1) there are 3 boys (who count as 3). The total number in the proportion is 3 + 1 =4. You are given a total, but that is both boys and girls. That's why you need the 4.
3/4 = x / 236 Cross multiply
4x = 3 * 236
4x = 708 Divide by 4
x = 708/4
x = 177
There are 177 boys at the school and 236 - 177 = 59 girls.
Each number is being multiplied by 3.
The required number is 19 given that -2 is added to a number, the sum is doubled and the result is -15 less than the number. This can be obtained by assuming the number as x, converting the given conditions to algebraic expression, forming algebraic equation and solving for x.
<h3>Find the required number:</h3>
Here in the question it is given that,
- The result is -15 less than the number
We have to find the required number.
Let the required number be x.
⇒ -2 is added to the number ⇒ -2 + x
⇒ the sum is doubled ⇒ 2(-2 + x)
⇒ the result is -15 less than the number ⇒ 2(-2 + x) = x -(-15)
2(-2 + x) = x + 15
⇒ - 4 + 2x = x + 15
⇒ x = 19
Hence the required number is 19 given that -2 is added to a number, the sum is doubled and the result is -15 less than the number.
Learn more about algebraic expression and equation here:
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