Wei Jie's answer to Syasya's Primary 6 Maths Speed Singapore question.

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Wei Jie
Wei Jie's answer
51 answers (A Helpful Person)
1st
J is 20cm/s faster than N, which means every second J will move 20cm more.
J finished the race in 12s. So J moved 20x12=240cm more than N in the 12s.
Since N only completed 2/3 while J finished the race, J moved 1/3 more than N.
So 1/3=240cm
Race=240x3=720cm