$MathMaster logo$

MathMaster

Home
general
4x21 using doubling twice strategy

Question

4x21 using doubling twice strategy

50

likes

250 views

Answer to a math question 4x21 using doubling twice strategy

$Expert avatar$

4.9

87 Answers

1. First doubling:

4 \times 21 = (2 \times 21) \times 2

2. Simplify inside the parentheses:

2 \times 21 = 42

3. Second doubling:

42 \times 2 = 84

Answer:

4 \times 21 = 84

Frequently asked questions (FAQs)

What is the value of log(e) - ln(e)?

+

What is the number of different ways to arrange 4 books on a shelf?

+

What is the value of x in the cubic equation 2x^3 + 4x^2 - 3x + 1 = 0?

+

New questions in Mathematics

A circular park has a diameter of 150ft. A circular fence is to be placed on the edge of this park. Calculate the cost of fencing this park if the rate charged is $7 per foot. Use π = 3.14.

I) Find the directional derivative of 𝑓(𝑥, 𝑦) = 𝑥 sin 𝑦 at (1,0) in the direction of the unit vector that make an angle of 𝜋/4 with positive 𝑥-axis.

Express the following numbers in decimal system, where the subscript indicates the base: 110101 (SUBINDEX=2)

Consider numbers from 1 to 2023. We want to delete 3 consecutive, so that the avarage of the left numbers is a whole number. How do we do that

Solve the math problem 400 students are asked if they live in an apartment and have a pet: Apartment: 120 Both: 30 Pet: 90 The probability that a randomly selected student not living in an apartment has a pet is

what is the annual rate on $525 at 0.046% per day for 3 months?

During a fishing trip Alex notices that the height h of the tide (in metres) is given by h=1−(1/2)*cos(πt/6) where t is measued in hours from the start of the trip. (a) Enter the exact value of h at the start of the trip in the box below.

What is 75 percent less than 60

A,B,C and D are the corners of a rectangular building. Find the lengths the diagonals if AB measures 38' - 9" and AD measures 56' - 3"

A contractor gives a bank note for $10250 at a rate of 1% for one month. How much interest is charged for 4 months?

In an orchard there are 360 trees and they are distributed in 9 rows with the same number of trees in each row. 2 are rows of orange trees, 4 of apple trees and the rest are of pear trees. What fraction of the trees in the orchard are of each type of fruit tree? How many trees of each type are there?

Write an expression using compatible numbers that can be used to estimate the quotient 629\86

A property sold for $745,000 in a co-brokered transaction. The seller has agreed to pay a 7% commission to the listing firm. The listing firm has agreed to equally split the commission with the selling firm. If the buyer’s broker will receive 8% of the selling firm’s commission, how much commission will the buyer’s broker receive? $14,900 $3725 $$37250 $18625

Consider mixing 150 ml, 0.1M, HCI with 100 ml, 0.2M, KOH solution. Determine the pH of final solution.

A membership to the gym cost $25 per person in 1995. The membership cost has increased by an average $6 per person for each year since 1995. Write a linear equation for the cost of a gym membership for one person since 1995. What is the cost of a gym membership in 2009?

How much does 7.2 moles of ammonium dichromate weigh? (NH4)2Cr2O7

a coffee shop has 9 types of creamer and 11 types of sweetener. In how any ways can a person make their coffee?

(3b)⋅(5b^2)⋅(6b^3)

Suppose a car license plate consists of 2 letters and two digits of which the first cannot be zero. How many different plates can be engraved? consider only 26 letters and 10 digits draw an example of this.