# Contributor lessons: Swarming Cicadas

## The Problem

In the United States, 2024 is a special year for periodical cicadas. In a rare event, billions of 17-year cicada nymphs (nymphs that have lived underground for exactly17 years) will emerge above ground at the same time as billions of 13-year cicada nymphs (nymphs hat have lived underground for exactly13 years).

**When will be the next year that both 13-year and 17-year cicada nymphs emerge at the same time?**

**Did you know?**

Surviving in the soil for 13 or 17 years can be difficult as pesticides and chemicals (sprayed onto lawns) can kill cicada larvae.

## Visualising the Problem and Getting Started

Salma said, “I will use addition to find the next year that the cicadas will emerge together.”

Dennis said, “I will use multiplication to find the next year that the cicadas will emerge together.”

**What will you do? Explain your reasoning to a partner.**