Exercises: Types of Numbers — Composite, Square, Cubic, and Triangular

Work through each section in order. Show your work where indicated.

Grade 7·19 problems·~30 min·Uganda NCDC Primary 7 Mathematics·lesson·patterns-02

Work through problems with immediate feedback

Fluency Practice

Use $T_n = \frac{n(n+1)}{2}$ to decide: is 28 a triangular number?

Yes — $T_7 = \frac{7 \times 8}{2} = 28$ .

No — no whole number $n$ gives $T_n = 28$ .

Yes — $28 = 4 \times 7$ , so it is triangular.