Controller down. Brain on.
Mission:
Number Island!
A tower of pizza boxes. A vegetable garden. And a high score board that is still missing your name.
Mental math on!
Big times tables, square numbers
Data, ordering, rounding
Everything mixed, on a new day
Big times tables · mental math tricks
Pizza Turbo
Wobbi delivers pizza all over the island. Break big multiplication problems into small ones you already know.
Split trick: tens and ones separately
Split the big number into tens and ones. Work out both parts and add them.
In c) and d) the order of the parts doesn’t matter.
Neighbor trick: use 20
19 is right next to 20. Multiply by 20 and subtract the number once.
Three problems, one trick.
Turnaround fact: 6 × 17 is the same as 17 × 6. So both tricks also work when the big number comes second.
Big times tables · forwards and backwards
Delivery HQ
At Delivery HQ every number has to be right. Otherwise the pizza ends up at the wrong house.
Delivery table
Always multiply the number on the left by the number on top. One box is filled in as an example.
| × | 4 | 7 | 9 |
|---|---|---|---|
| 12 | 48 | ||
| 15 | |||
| 17 | |||
| 18 |
Multiply by 10 first. Then subtract the number once.
18 × 9 = 18 × 10 − 18 = 180 − 18 = 162
Eleven boxes are waiting for you.
Work backwards
Which number is missing? Think of the matching multiplication fact.
Six blanks.
Mistake Detective
Pixel was too fast. Exactly 3 answers are wrong. Check “wrong” for those and write the correct answer in the box.
Only the wrong problems need a correction.
Pro round: both numbers above 10
Split the second number: 12 × 13 = 12 × 10 + 12 × 3 = 120 + 36 = 156
Four problems for pros.
Square numbers up to 20
Square Gardens
On the island every vegetable bed is a square: as many rows as plants in each row. A bed with 4 rows of 4 plants has 4 × 4 = 16 plants. 16 is a square number.
All the beds up to 20
Multiply each number by itself. You know the top row from the basic times tables.
20 boxes. The bottom row is the important one.
Staircase trick: the bed grows
This is how a 15-bed becomes a 16-bed: a new row of 15 plants at the bottom and a new column of 16 plants on the right (counting the corner). That is 15 + 16 = 31 new plants, so 16 × 16 = 225 + 31 = 256. Keep going up to 20 × 20. Fill in the jumps and the square numbers.
Check: it has to end at 400.
Square number or not?
Compare your explanation for e) with the answer key yourself.
Garden job
Two questions.
Short form: 15 × 15 = 15² (say: “15 squared”). Square numbers from 11² to 20² are worth learning by heart.
Collecting and showing data
Island Survey
Pixel asked 30 people on the island: “Which job do you like best?” Each answer is a letter in this list.
Tally chart and table
Make one mark for each answer. Draw the 5th mark across the first four: Then count and write the number.
| Job | Tally marks | Number |
|---|---|---|
| PPizza delivery | ||
| IIce cream sales | ||
| TTaxi driving | ||
| FFishing | ||
| RFire rescue | ||
| Total |
Tip: check off the letters above as you count.
Bar graph
Draw one bar for each job. 1 square = 1 person. On screen: click in the column.
Check: all bars together must be 30 squares tall.
Draw first, then answer the questions.
Comparing and ordering numbers
High Score Board
In the island arcade every point counts. Who is ahead, who is just behind?
Number before and after
The number before is 1 less, the number after is 1 more. Fill in the blanks.
| Number before | Number | Number after |
|---|---|---|
| 599 | ||
| 4,000 | ||
| 10,909 | ||
| 7,099 | ||
| 20,000 |
Ten blanks.
Greater or less?
Write < or >. The point faces the smaller number.
For two of them you need to calculate first.
Sort the high scores
Put the scores in order. Start with the smallest.
Same digits, different order. Look closely!
Number line
Which numbers belong to A, B, C and D? Then mark 140 and 320 with an arrow below the line. On screen: click on the line.
Think first: how big is one small step?
Rounding
Rounding Radar
Island Radio only says rounded numbers. But they have to be rounded correctly!
2,718 ≈ 2,700 (nearest hundred: the digit to the right is 1, so round down). The sign ≈ means “about”.
To the nearest ten, hundred, thousand
| Number | nearest ten | nearest hundred | nearest thousand |
|---|---|---|---|
| 4,352 | |||
| 7,865 | |||
| 2,996 | |||
| 15,049 |
Twelve boxes.
Rounding puzzle
A whole number was rounded. What is the smallest and the greatest number it could have been?
Four limits.
Radio check
The island festival had 12,468 guests. The radio says: “About 12,500 guests!”
Three questions.
Watch out, trap: Always round from the original number. 1,449 to the nearest hundred is 1,400. Don’t round to 1,450 first and then to 1,500!
All mixed · no hints
Boss Level: Island Champion
Everything mixed, like a test. Work on your own first, then compare with the answer key.
Speed round
Goal: 3 minutes 3:00Solve everything first, then check.
Job money
Wobbi drives a taxi 8 times and gets 14 coins for each ride. Pixel delivers 9 pizzas and gets 13 coins for each pizza.
Six boxes.
Ice cream truck graph
Ice creams sold from Monday to Friday. From one line to the next is 20 ice creams.
Four questions.
Number riddle
I am a square number between 300 and 400. My digit sum is 10.
Digit sum of 225: 2 + 2 + 5 = 9
Solve first, then check.
How am I doing?
After checking, color in: green, yellow or red.
Bonus round · on screen only
Endless Trainer
New problems every time. Press Enter to check. How long can your streak get?
The check buttons show how many boxes are correct. Compare your strategies and explanations with the answer key yourself.
ANSWER CHECKPOINT · Work it out first, then compare.
Answers: missions 1 to 4
1 · Pizza Turbo
c) 90 + 54 = 144 · d) 80 + 24 = 104
B a) 120 − 6 = 114 · b) 160 − 8 = 152 · c) 180 − 9 = 171
Typical mistake: multiplying only the ones and forgetting the ten. 14 × 7 is not 4 × 7 + 10 = 38.
2 · Delivery HQ
| × | 4 | 7 | 9 |
|---|---|---|---|
| 12 | 48 | 84 | 108 |
| 15 | 60 | 105 | 135 |
| 17 | 68 | 119 | 153 |
| 18 | 72 | 126 | 162 |
Check with multiplication: 15 × 9 = 135, 16 × 6 = 96, 19 × 9 = 171.
D 11 × 17 = 187 · 14 × 15 = 210 · 16 × 12 = 192 · 13 × 14 = 182
Where the mistakes come from: 14 × 6 = 60 + 24 = 84 (forgot the ten when adding). 16 × 7: 10 × 7 is 70, not 60. 15 × 8 = 80 + 40 = 120.
3 · Square Gardens
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 4 | 9 | 16 | 25 | 36 | 49 | 64 | 81 | 100 |
| 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
| 121 | 144 | 169 | 196 | 225 | 256 | 289 | 324 | 361 | 400 |
C 196 = 14 × 14 · 289 = 17 × 17 · 361 = 19 × 19
d) 289 (300 − 289 = 11, but 324 − 300 = 24)
e) No. 15 × 15 = 225 and 16 × 16 = 256 are square numbers next to each other. 250 is between them, so no number times itself makes 250.
D a) 13, because 13 × 13 = 169 · b) 225 − 169 = 56 seedlings
4 · Island Survey
| Job | Tally | Number |
|---|---|---|
| Pizza delivery | 9 | |
| Ice cream sales | 7 | |
| Taxi driving | 3 | |
| Fishing | 6 | |
| Fire rescue | 5 | |
| Total | 30 |
1. Pizza delivery · 2. 9 − 3 = 6 · 3. Taxi and fishing (3 + 6 = 9)
Common mistakes: letters counted twice or not at all. So always check: total = 30. In a group of five, the line across is the fifth mark, not a sixth.
Answers: missions 5 to 7
5 · High Score Board
598 | 599 | 600
3,999 | 4,000 | 4,001
10,908 | 10,909 | 10,910
7,099 | 7,100 | 7,101
19,998 | 19,999 | 20,000
(12 × 9 = 108 and 13 × 13 = 169)
A = 60 · B = 240 · C = 380 · D = 460
140: two small marks after 100. 320: one small mark after 300.
Trap: the number before 4,000 is 3,999, not 3,000 or 4,999. The number before 19,999 is 19,998.
6 · Rounding Radar
| Number | Ten | Hundred | Thousand |
|---|---|---|---|
| 4,352 | 4,350 | 4,400 | 4,000 |
| 7,865 | 7,870 | 7,900 | 8,000 |
| 2,996 | 3,000 | 3,000 | 3,000 |
| 15,049 | 15,050 | 15,000 | 15,000 |
C 1. nearest hundred · 2. 12,000 · 3. nearest ten
2,996 to the nearest ten: the digit to the right is 6, so round up. 99 becomes 100, so 3,000. 15,049 to the nearest hundred is 15,000, not 15,100: don’t round in steps!
7 · Boss-Level
| 16 × 7 = 112 | 19 × 4 = 76 | 14 × 14 = 196 |
| 12 × 9 = 108 | 18 × 8 = 144 | 17 × 17 = 289 |
| 15 × 6 = 90 | 13 × 7 = 91 | 120 ÷ 15 = 8 |
| 12 × 15 = 180 | 153 ÷ 17 = 9 | 18 × 18 = 324 |
b) 112 + 117 = 229 coins. 250 − 229 = 21.
Answer: They don’t have enough. They still need 21 coins.
Mistake guide
- Times table mistakes in the speed round: redo missions 1 and 2, then 5 minutes of speed round every day.
- Square numbers shaky: cover the table from mission 3 and say them out loud until 11² to 20² stick.
- Graph misread: first figure out what one square or one line stands for.
- Ordering, rounding: compare numbers place by place from the left. When rounding, look only at the one digit to the right.
For grown-ups: ask the child to explain how they worked it out first. A correct strategy with a small slip is a good step. Word problems need an answer sentence, as in mission 7 B.