For a fixed material, heat is directly proportional to both mass and temperature change. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Start from the base case
The base case needs 30 joules of heat.
Qbase=30J
Double the mass
Keeping the material and warming the same, doubling mass doubles the heat to 60 joules.
Qmore mass=2⋅30J=60J
Double the temperature change
Keeping the mass and material the same, doubling the temperature change also gives 60 joules.
Qmore warming=2⋅30J=60J
Either doubled factor doubles the heat
The bars show three comparable cases on one scale. Mass and temperature change are separate factors, but each is direct.