Olympiad Maths Prep

Track / Stage 3 / 149 of 260 #149 of 2000

Problem 149

AMC 10/12, early questions
Algebra Difficulty 3.5 Find the answer

Calculate:(1)20+3+57(1)-20+3+5-7;(2)(32)÷4×14(2)(-32)÷4×\frac{1}{4};(3)(2714)×28(3)(\frac{2}{7}-\frac{1}{4})×28;(4)24×[(3)×(2113)(5)]÷(25)2(4)-{2}^{4}×[(-3)×(-2-1\frac{1}{3})-(-5)]÷{(-\frac{2}{5})}^{2}.

Official solution

### Step-by-Step Solution

#### Problem (1): 20+3+57-20+3+5-7

- Start by adding and subtracting the numbers in order:
20+3+57-20 + 3 + 5 - 7
- Combine the positive numbers and then the negative ones:
=(207)+(3+5)= (-20 - 7) + (3 + 5)
- Simplify the operations:
=27+8= -27 + 8
- Finally, add the results:
=19= -19
- So, the answer is 19\boxed{-19}.

#### Problem (2): (32)÷4×14(-32)÷4×\frac{1}{4}

- Begin by dividing 32-32 by 44, then multiply by 14\frac{1}{4}:
=(32)÷4×14=(-32) ÷ 4 × \frac{1}{4}
- Perform the division first:
=8×14= -8 × \frac{1}{4}
- Then, multiply by 14\frac{1}{4}:
=2= -2
- Therefore, the answer is 2\boxed{-2}.

#### Problem (3): (2714)×28(\frac{2}{7}-\frac{1}{4})×28

- Start by finding the common denominator and subtracting the fractions:
=(2714)×28= \left(\frac{2}{7} - \frac{1}{4}\right) × 28
- Convert 14\frac{1}{4} to 728\frac{7}{28} and 27\frac{2}{7} to 828\frac{8}{28}, then subtract:
=(828728)×28= \left(\frac{8}{28} - \frac{7}{28}\right) × 28
- Simplify the fraction and multiply by 2828:
=128×28= \frac{1}{28} × 28
- The result is:
=1= 1
- Hence, the answer is 1\boxed{1}.

#### Problem (4): 24×[(3)×(2113)(5)]÷(25)2-{2}^{4}×[(-3)×(-2-1\frac{1}{3})-(-5)]÷{(-\frac{2}{5})}^{2}

- Begin by simplifying the expression inside the brackets and the exponent:
=16×[(3)×(103)(5)]÷425= -16 × [(-3) × (-\frac{10}{3}) - (-5)] ÷ \frac{4}{25}
- Simplify the multiplication and addition inside the brackets:
=16×(10+5)×254= -16 × (10 + 5) × \frac{25}{4}
- Multiply the numbers:
=16×15×254= -16 × 15 × \frac{25}{4}
- Simplify to find the final result:
=1500= -1500
- Therefore, the answer is 1500\boxed{-1500}.

Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic, difficulty and ordering added by this site.