# Math activity

A `math`

activity computes an arithmetic expression using the message's
attributes. The expression must return a number. For example, given the following input
message:

`{ "tempF": 50, }`

after processing by the following `math`

activity:

`{ "math": { "name": "MyMathActivity", "math": "(tempF - 32) / 2", "attribute": "tempC", "next": "MyDatastoreActivity" } }`

the resulting message looks like:

`{ "tempF" : 50, "tempC": 9 }`