1)* Remember the general equation for alpha decay is:

* And the general equation for beta decay is:

2) * Click here for a big tip.

* Would there still be a large proportion of the sample remaining in a very old geological specimen?

3) * Try dividing the N_d formula by the N_p formula.

4) * Do you want to see the solution?

6) * At the intercept the value of ⁸⁷Rb / ⁸⁶Sr is zero, what does this mean?

7) * If you want to compare, I got a gradient of 0.054 and an intercept of 0.7

8) * Click here for a VERY big tip.

9) * As a check, my graph had a gradient of 0.0033 and an intercept of 0.51226

10) * The minerals that are in equilibrium all have similar ratios of ¹⁴³Nd / ¹⁴⁷Sm, because the initial ratio and the initial rate of decay would be the same for all minerals.

12) * Think about plate tectonics.

13) * Minerals in a meteorite can be considered to be in an isolated system, can the minerals in the Earth?