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Practice
Decimals

Normal

Decimals: Difficult Problems with Solutions

By Catalin David

Problem 1

1 + 1.1 + 1.11 + 1.111 + 1.1111 + 1.11111 + 1.111111 =

Solution:
1 + 1.1 + 1.11 + 1.111 + 1.1111 + 1.11111 + 1.111111 = 7.654321

Problem 2

3.5 + 4.5 × 2 =

Solution:
3.5 + 4.5 × 2 = 3.5 + 9 = 12.5

Problem 3

(3.5 + 4.5) × 2 =

Solution:
(3.5 + 4.5) × 2 = 8 × 2 = 16

Problem 4

2.4 ×[2.5 × (1.37 + 0.63)]=

Solution:
2.4 ×[2.5 × (1.37 + 0.63)]= 2.4 × (2.5 × 2) = 2.4 × 5 = 12

Problem 5

28.37 + 15.59 + 45.63 + 27.41 =

Solution:
In some cases it's easier to calculate in this way:
(28.37 + 45.63) + (15.59 + 27.41)= 74 + 43 = 117

Problem 6

3.4 × 2.7 + 3.4 × 2.3 =

Solution:
Because 3.4 is repeated in both multiplication, we can calculate easier this way.
3.4 × 2.7 + 3.4 × 2.3 = 3.4 × (2.7 + 2.3) = 3.4 × 5 = 17

Problem 7

18.36 × 10 + 0.6172 × 100 =

Solution:
18.36 × 10 + 0.6172 × 100 = 183.6 + 61.72 = 245.32

Problem 8

2.4 + 2.4 ÷ 0.3 + 0.3 × 2.4 =

Solution:
We first do the multiplication and the division.
2.4 + 2.4 ÷ 0.3 + 0.3 × 2.4 = 2.4 + 8 + 0.72 = 11.12

Problem 9

137.6 ÷ 10 - 672.81 ÷ 100 =

Solution:
137.6 ÷ 10 - 672.81 ÷ 100 = 13.76 - 6.7281 = 7.0319

Problem 10

(32.81 + 174.5) × (49.37 + 50.63) =

Solution:
(32.81 + 174.5) × (49.37 + 50.63) = 207.31 × 100 = 20731

Problem 11

4x - 1.5 = 5 × 0.5
Find x = ?

Solution:
4x - 1,5 = 5 × 0,5
4x - 1,5 = 2,5
4x = 2,5 + 1,5
4x = 4
x = 1

Problem 12

1.1 + 2.2 + 3.3 + 4.4 + 5.5 + 6.6 + 7.7 + 8.8 + 9.9 =

Solution:
It's easier to calculate in this way.
1.1 + 2.2 + 3.3 + 4.4 + 5.5 + 6.6 + 7.7 + 8.8 + 9.9 = (1.1 + 9.9) + (2.2 + 8.8) + (3.3 + 7.7) + (4.4 + 6.6) + 5.5 = 11 + 11 + 11 + 11 + 5.5 = 49.5

Easy

Normal

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