There are
18 girls and
22 boys in a class, one
of them has a letter. The probability that
the
owner
of the letter is a boy is

First take the total of students ( 18 + 22 ) = 40. To calculate the percentage take the total of boys and divide it by the total of 40, and multiply by 100%. That gives 22 : 40 x 100% = 55. So the probability that a boy has the letter is 55%.

the law of definite proportions states samples of a compound will always contain the same proportion of elements by mass. in other words, a given compound will always contain the same elements in the same proportions by mass.the law of multiple proportions states when two elements combine with each other to form more than one compound, then the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.