Question

The table shows how the number of sits-ups Marla does each day has changed over time. At this rate, how many sits-ups will she do on Day 12? Explain your steps in solving this problem.

Answer 1

Answer

61

Step-by-step explanation

Given that every day Marla does 4 more sit-ups than the previous day, then the number of sit-ups can be modeled by an arithmetic sequence.

Arithmetic sequence formula

$a_n=a_1+(n-1)d$

where

• aₙ: nth term

,

• a₁: first term

,

• d: common difference

The common difference is found by subtracting two consecutive terms as follows:

$d=21-17=4$

Substituting a₁ = 17, n = 12 and d = 4, the number of sit-ups on Day 12 are:

$\begin{gathered} a_{12}=17+(12-1)4 \\ a_{12}=17+11\times4 \\ a_{12}=17+44 \\ a_{12}=61 \end{gathered}$