Radioactive dating is a technique used to date specimens of igneous rock. Elements vary in form based on the difference in the number of neutrons in the atom’s nucleus. These various forms are called isotopes. Some isotopes are radioactive and can be used to date rocks using their known half-life, the amount of time for the original number of atoms to fall to half its original value. Different minerals contain different radioactive isotopes. Once the rock has cooled, radioactive decay begins, and the original, or parent, atoms begin to decay and form daughter atoms. The parent-to-daughter proportion of atoms in a substance can tell us how many half-lives have occurred. The number of half-lives is multiplied by the length of one half-life, and the age of the substance is revealed. The chart below shows the parent isotopes, daughter isotopes, and the half-life of the parent isotopes.

the anwser is d) 75°

step-by-step explanation:

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step-by-step explanation:

ratios represent a pattern or relationship that can be scaled.

equivalent ratios are pairs of ratios that represent the same relationship between quantities, and can be generated by multiplying or dividing both quantities in the ratio by the same factor.

in this lesson, students will use double number lines and ratio reasoning to solve ratio problems. by partitioning double number lines into proportionate intervals, students will build an understanding of equivalent ratio relationships as those that are generated by multiplying or dividing two related quantities by the same number. this lesson will build upon students' prior understanding of multiplicative comparisons, number line reasoning and equivalent fractions (while highlighting the difference between equivalent fractions and equivalent ratios); and will build toward future work in this unit on building ratio tables, and work in future grades in proportionality, scaling, and expressing and graphing linear functions.

step-by-step explanation:

ratios represent a pattern or relationship that can be scaled.

equivalent ratios are pairs of ratios that represent the same relationship between quantities, and can be generated by multiplying or dividing both quantities in the ratio by the same factor.

in this lesson, students will use double number lines and ratio reasoning to solve ratio problems. by partitioning double number lines into proportionate intervals, students will build an understanding of equivalent ratio relationships as those that are generated by multiplying or dividing two related quantities by the same number. this lesson will build upon students' prior understanding of multiplicative comparisons, number line reasoning and equivalent fractions (while highlighting the difference between equivalent fractions and equivalent ratios); and will build toward future work in this unit on building ratio tables, and work in future grades in proportionality, scaling, and expressing and graphing linear functions.