1. Basic Mathematical Skills

Basic Mathematical Skills Operations with Decimals Frengie G. Botoy Jagupit NHS, Philippines

Addition of Decimals To add decimals, arrange the numbers so that their decimal points fall in a column. Then perform the operation.

Example 27.93 + 6.4 ► First line up the decimal places, then perform the operation

+

27.93 6.4 34.33

Subtraction of Decimal 23.07 – 2.3 ► First line up the decimal places, then perform the operation

-

23.07 2.3 20.77

Multiplication of Decimals • Multiply the multiplicand by the multiplier • the product will have a many as the combined decimal places of both the multiplicand and multiplier.

Example 0.47 X .7

multiplicand

multiplier

0.329

product

Division of Decimals ►To

divide a decimal with whole number, divide the dividend by the divisor

►The

quotient has the same number of decimal places as that in the dividend

ex.

divisor

0.081 7 0.567 0 56 56 7 7 0

quotient dividend

Rounding Off Numbers and Decimals If the number to be dropped is between 0 and 4, round down the numbers preceding it and replace all digits that follow with zeroes.

Examples: 453

450 (nearest ten)

6.754 hundredth)

6.75 (nearest

432 hundred)

400 (nearest

Rounding Off Numbers and Decimals If the number to be dropped is between 6 and 9, round up the numbers preceding it and replace all digits that follow with zeroes.

Examples: 237

240 (nearest ten)

25.687 hundredth)

25.69 (nearest

2967 thousand)

3000 (nearest

Rounding Off Numbers and Decimals If the number to be dropped is exactly 5 and it is preceded by an even number retain the preceding number

Examples: 345 23.65 985

340 (nearest ten) 23.6 (nearest tenth) 980 (nearest ten)

Rounding Off Numbers and Decimals If the number to be dropped is exactly 5 and it is preceded by an odd number, add 1 to the preceding number

Examples: 315

320 (nearest ten)

23.35

23.4 (nearest tenth)

975

980 (nearest ten)

Addition of Integers A. The sum of two integers with like signs is the sum of their absolute values with the common sign prefixed before the sum.

Ex.

(-14) + (-7) = -21 (+3) + (+2) = +5

B. The sum of two integers with different signs is the difference of their absolute values with the sign of the integer of larger absolute value prefixed before the difference.

Ex. (-14) + (+2) = -12

(-12) + (+28) = +16

Subtraction of Integers To subtract two integers, change the sign of the subtrahend and proceed with the process of addition.

Ex. (-14) – (+8) = -22 (+35) – (-15) = +50 (-12) – (-28) = +16

Multiplication of Integers The product of two integers having like signs is positive

Ex.

(-5) x (-2) = +10 (2) x (10) = 20

Multiplication of Integers The product of two integers having unlike signs is negative.

Ex. (-4) x (7) = -28 (+12) x (-5) = -60

Division of Integers The quotient of two integers having like signs is positive.

Ex. (-12) / (-4) = +3 (12) / (4) = 3

Division of Integers The quotient of two integers having unlike signs is negative.

Ex. (+12) / (-4) = -3 (-15) / (5) = -3

The End