Ratios and Proportions

Knowing how to use ratios and ratios is very useful in chemistry courses, especially when using different measurement units. Let's start with the definition of the dictionary.

Ratio: Relative size of two quantities. It is expressed as the quotient divided by others and the ratio of b to a is expressed as a: b or a / b.

In 1995, 78 women entered chemistry at high school and 162 men entered. What is the ratio of women to men? A man from a woman?

Use the divide key to reduce the score (Cancellation factor 6), or use a formula equivalent to the decimal number of these scores.

By writing answers in these ways, we lose the information, the exact number of men and women. Be careful! For example, given a ratio of 13: 27, there is a possibility that the score has decreased, so the original number may increase. This brings us to the scale

If the corresponding scores are equal, the ratio is considered to be proportional. What I actually did above is that the score of 78/162 is equal to the score of 13/27. To get the second ratio, you can divide the two numbers of the first ratio by six.

These two equations are examples of ratios (equal proportions); that is very simple. How to use ratios Let's add another question to the question.

The number of boys enrolled in 1996 was 193, but the proportion of men and women registered in the chemistry course was almost the same as in 1995. How many women participated in the 1996 chemistry course?

These are the easiest to solve when writing in fractions. Note that x was used as a variable in normal algebra, so we used x for unknown women.

The number of women registered in 1996 is 92.9259259. Since the proportion of women entering and leaving is not small, we will report 93 (correctly rounded up to 92.9259259). It may be prudent to say "About 93 women participated in chemistry in 1996". The problem of yen also appears in chemistry. The object to be counted is usually atom or atomic particle such as proton, neutron, electron etc. In this case, only the integer answer makes sense. However, in some cases, even a small amount (such as quality) may be measured. Then you should use the rules to appropriately round and review critical data in the session

The mass to charge ratio of the isotope of a particular element is determined to be 97 × 10 -7 kg per coulomb. If the charge of the isotope is 614 × 10 -19 coulombs, how much is the mass of the isotope?

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"Adjust" the ratio using 2 multiplication or division. A common type of problem with ratios involves using ratios to scale up or down two numbers. The ratio of all items that multiplies or divides a ratio by the same numerical value is the same as the original scale. Therefore, to scale the ratio, multiply or divide by the scale factor.

Ratios are around us, just comparing the two numbers each day (eg red fondant vs. Yellow Fondant). Scale is a statement that allows you to find unknown ratios from known ratios. With known ratios, I know these two numbers. With an unknown proportion, you only know one of the numbers. To solve the unknown, set the known ratio on one side and the ratio of unknown ratio on the other side, cross multiplication and solve the obtained equation. This method is always valid as long as it properly identifies known ratios and unknown ratios.