(i) Write down the 4th term of this sequence of numbers.\[1 \qquad 4 \qquad 9 \qquad \ldots\ldots \qquad 25 \qquad 36 \qquad 49\]
[1]
(ii) Write down the name for the sequence of numbers. [1]
(b)
(i) Amit draws these four diagrams. Amit writes the number of dots on the perimeter underneath each diagram.
Amit says
My diagrams show the first four triangular numbers.
Complete this statement.
Amit is incorrect because ...................................................... [1]
(ii) Use the grid below to draw the correct diagram for the 5th triangular number.
[1]
Mark scheme (a)
Answer
Marks
Part marks and guidance
(i) 16
1
(ii) Square [numbers]
1
Accept e.g. squared Do not accept \(n^2\) oe
Mark scheme (b)
Answer
Marks
Part marks and guidance
(i) All the dots in the triangle should be filled in/counted oe or There should be 10 [dots] oe or 9 is not a triangular number oe
1
(ii) Correct diagram of 15 dots
1
Ignore any numbers and mark diagram Diagram correct by eye with 15 dots drawn in correct arrangement. Ignore connecting lines, wobbles, different size dots but not extra dots unless clearly discarded/erased
