When we add we count up. We have \(\displaystyle 1\) triangle in the first box, and then \(\displaystyle 1\) triangle in the second box. In total we have \(\displaystyle 2\) triangles. If you start at \(\displaystyle 1\) on a number line and count up \(\displaystyle 1\), you have \(\displaystyle 2\).

\(\displaystyle 1, 2\)

When we add we count up. We have \(\displaystyle 1\) triangle in the first box, and then \(\displaystyle 3\) triangles in the second box. In total we have \(\displaystyle 4\) triangles. If you start at \(\displaystyle 1\) on a number line and count up \(\displaystyle 3\), you have \(\displaystyle 4\).

\(\displaystyle 1, 2,3,4\)

When we add we count up. We have \(\displaystyle 1\) triangle in the first box, and then \(\displaystyle 2\) triangles in the second box. In total we have \(\displaystyle 3\) triangles. If you start at \(\displaystyle 1\) on a number line and count up \(\displaystyle 2\), you have \(\displaystyle 3\).

\(\displaystyle 1, 2,3\)

When we add we count up. We have \(\displaystyle 1\) triangle in the first box, and then \(\displaystyle 4\) triangles in the second box. In total we have \(\displaystyle 5\) triangles. If you start at \(\displaystyle 1\) on a number line and count up \(\displaystyle 4\), you have \(\displaystyle 5\).

\(\displaystyle 1, 2,3,4,5\)

When we add we count up. We have \(\displaystyle 1\) triangle in the first box, and then \(\displaystyle 5\) triangles in the second box. In total we have \(\displaystyle 6\) triangles. If you start at \(\displaystyle 1\) on a number line and count up \(\displaystyle 5\), you have \(\displaystyle 6\).

\(\displaystyle 1, 2,3,4,5,6\)

When we add we count up. We have \(\displaystyle 1\) triangle in the first box, and then \(\displaystyle 6\) triangles in the second box. In total we have \(\displaystyle 7\) triangles. If you start at \(\displaystyle 1\) on a number line and count up \(\displaystyle 6\), you have \(\displaystyle 7\).

\(\displaystyle 1, 2,3,4,5,6,7\)

When we add we count up. We have \(\displaystyle 1\) triangle in the first box, and then \(\displaystyle 7\) triangles in the second box. In total we have \(\displaystyle 8\) triangles. If you start at \(\displaystyle 1\) on a number line and count up \(\displaystyle 7\), you have \(\displaystyle 8\).

\(\displaystyle 1,2,3,4,5,6,7,8\)

When we add we count up. We have \(\displaystyle 1\) triangle in the first box, and then \(\displaystyle 9\) triangles in the second box. In total we have \(\displaystyle 10\) triangles. If you start at \(\displaystyle 1\) on a number line and count up \(\displaystyle 9\), you have \(\displaystyle 10\).

\(\displaystyle 1, 2,3,4,5,6,7,8,9,10\)

When we add we count up. We have \(\displaystyle 1\) triangle in the first box, and then \(\displaystyle 0\) triangles in the second box. In total we have \(\displaystyle 1\) triangle. If you start at \(\displaystyle 1\) on a number line and count up \(\displaystyle 0\), you are still at \(\displaystyle 1\).

\(\displaystyle 1\)

When we add we count up. We have \(\displaystyle 2\) triangles in the first box, and then \(\displaystyle 1\) triangle in the second box. In total we have \(\displaystyle 3\) triangles. If you start at \(\displaystyle 2\) on a number line and count up \(\displaystyle 1\), you have \(\displaystyle 3\).

\(\displaystyle 2,3\)