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Maths · Number

Add whole numbers or decimals

Calculate one addition with aligned place values.

Free to use and free to share. There is no sign-up, no score, and nothing a child does here is recorded or sent anywhere.

Practise it now

Every brick is the two bricks below it added together. Tap a gap and fill in all three.

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A worked example

One question of the kind this skill is tested with, worked all the way through: the reasoning, and what the wrong answers are there to catch.

Adding to a value read off the line

Point B is marked on the number line. What is the total of the value at B and 4.5?

Each small step on this line is worth 0.1, and every labelled tick is ten steps on.

  1. 6.2
  2. 10.7
  3. 7.2
  4. 6.3

Answer: 6.2

How you get there

B sits at 1.7, so the sum is 1.7+4.5=6.2. Line the decimal points up under each other, not the last digits, because a digit only ever adds to a digit in the same place-value column.

Why the other answers tempt

Line the decimal points up under each other, not the last digits.

If they are stuck, say this

Work out what B is worth first by counting the small steps on from the labelled tick before it, then add 4.5 to it.

Now do it live in Build the Wall

How each of these 2 exercises teaches it

Build the Wall

Every brick is the two bricks below it added together. Tap a gap and fill in all three.

A number pyramid is just addition stacked up, but the order matters. Each brick needs BOTH bricks underneath it before you can work it out, so you always build from the bottom up. Here the bottom row 3, 5, 2, 6 gives 8, 7, 8 on the next row, then 15 and 15, and finally 30 on top. When a gap looks impossible, it is almost always because a brick below it is still missing. Fill that one first and the rest falls out.

What to say if they get stuck

  1. Start at the bottom. A gap can only be filled once you can see both bricks holding it up.
  2. The gap on the third row sits directly on 5 and 2 from the bottom row.
  3. With the third row finished you have 8, 7, 8. That gives 8+7 and 7+8 on the next row, and the capstone is those two added together.

Open Build the Wall on its own page to share it

Bar Model Builder

Drag the number bricks into the bar model, then read off the answer.

This engine’s own main skill is Bar Models: Missing Part. It practises add whole numbers or decimals alongside it.

The whole is fixed at 142. The parts you already know fill 97 of it, so the empty piece must be 14297=45.

What to say if they get stuck

  1. Drag every brick into the model first - the picture does the thinking.
  2. The parts you know sit inside the whole. The gap that is left over is what you are looking for.
  3. The ? brace marks the empty piece of the whole bar. Read the numbers on the bars underneath it.

Open Bar Model Builder on its own page to share it

Where add whole numbers or decimals sits in the 11+

The 11+ does not test these skills in isolation, and practising one in the wrong order wastes the practice. These are the skills the curriculum map connects this one to.

This is one piece of

Solve a multi-step problem

A multi-step context may compose an addition step.

How add whole numbers or decimals differs from the skills beside it

The same exercise practises several skills, and telling them apart is often the difficulty rather than the exercise itself. On this page the skill is: calculate one addition with aligned place values, and it stops where operation is supplied.

Related maths skills

All maths 11+ skills

Questions parents ask about add whole numbers or decimals

Answered from what the skill map records about this skill, not from a template. Every answer here is on the page, and the same questions are the page's FAQ structured data.

Calculate one addition with aligned place values. It is one of 55 named maths skills in the 11+, in the number strand, and this page carries 2 interactive exercises that practise it.

Knowing which maths topic to practise is most of the work

A free diagnostic covers arithmetic, fractions, geometry, measure and data handling, and comes back with the topics to spend the next few weeks on.