hey guys, was wondering what formula to use for this question and why. cheers
Hey RuskiBrah,
For (a): Use the formula for the sum of a geometric series:
a=45, n=6, r=0.4 (so make sure to use to the correct formula; -1<r<1).
Why? Initial height (first term) is 45 cm. Common ratio, r is 0.4: "grows by 2/5 of its previous growth each month". n in this case is the number of months so is equal to 6.
Your answer should be 74.7 cm.
For (b): Use the formula for limiting sum of an infinite geometric series:
a=45 and r=0.4
Why? The question is asking for the lamb's "final height" and for geometric series where -1<r<1, you can find its limiting sum because the series converge.
Your answer should be 75 cm.
Hope that helps! Let me know if you need any further explanations