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primary 5 | Maths
| Angles & Geometry

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To get to middle block of Row 13 from Row 5 , we count the number of blocks.

Below Row 5 , there's Row 6,7,8,9,10,11,12 and 13. From row 6 to 12, there's (6+7+8+9+10+12) = 63 blocks

In row 13, there are 13 blocks. The middle block is the 7th block.

So, from Row 6 to to the middle block of Row 13, there are 63 + 7 blocks = 70 blocks.

This tells you that there are 70 blocks ahead of the last block in Row 5

(moving across a row from left to right, going down row by row)

Notice that each time we move to the next

block, the number increases by 2.

Since there are 70 blocks ahead of the last block of Row 5 (number 29),

70 x 2 = 140

The middle block of Row 13 is bigger than the last block of Row 5 by 140.

29 + 140 = 169

The number in the middle of row 13 is 169.

Using this method, you can find the number of any block in the question, instead of only certain blocks

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