Im losing my mind how iss the answer 1225 and not 1224??????

[long stag]

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[austere ether]

6+9=15, so the last digit has to be 5

[austere ether]

the triangular numbers arent arithmetic.

[cerulean flare]

where are you getting the 9 from?

[austere ether]

1176+49

[cerulean flare]

oh we haven't done triangular numbers

[austere ether]

why are you attempting this problem that solely uses knowledge of triangular numbers then?

[cerulean flare]

its an exam paper

[austere ether]

so then... skip it

[cerulean flare]

its alr ill just learn it quickly

[austere ether]

if you know you dont know the knowledge