Jun Heng's answer to shu's Secondary 1 Maths Singapore question.

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Jun Heng
Jun Heng's answer
37 answers (Tutor Details)
1st
Number triangle with 3 dots = 1
Number triangle with 4 dots = 1+3 = 4
Number triangle with 5 dots = 1+3+6 = 10
Number triangle with 6 dots = 1+3+6+9 = 19
Number triangle with 7 dots = 1+3+6+9+12 = 31

Formula is t = (1/2)(3d²–15d+20)