Month: August 2012

Gooru: A New Online Learning Site Worth Trying

Resources and Freebies

Gooru is a new learning resource, a search engine that allows users to explore more than 2600 study guides. The guides cover topics from Grades 5 to 12 math and science.  It includes electronic instructional materials such as digital textbooks, animations, instructional videos, and more.

Gooru adapts to the user. It monitors the user’s learning progress and suggests appropriate resources and study guides.  It is also a social network, so you can connect with fellow learners worldwide. It has an online forum that allows users to post questions.

Gooru takes advantage of the Open Educational Resources (OER) to deliver its content free of charge. It is currently in Beta state, but allows online registration. 

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Common Errors in MDAS Operations

High School Algebra, High School Mathematics

The order of operations of multiplication, division, addition, and subtraction (MDAS) seems a very basic concept, but it is one of the source of misconceptions. The two errors below are very common.

Error 1: Addition must be performed before subtraction.

This is not always the case.  If addition and subtraction are adjacent operations, the operations must be performed from left to right. For example, although addition and subtraction are both present in

5 - (-2) + 7

subtraction must be performed first. Performing the operation, we have

5 - (-2) + 9 = 7 + 9 = 16.

Error 2: Multiplication must be performed before division.

Similar to addition and subtraction, if multiplication and division are adjacent operations, the operation which comes first must be performed. For example, in

6 \div 2 ( 1 + 2) .

you must divide 6 by 2 first, before multipying it by (1 + 2).

Therefore,

6 \div 2 (1 + 2)= 6 \div 2 (3) = 3(3) = 9.

For my Filipino readers, Sipnayan, a math blog written in Filipino, has a more extensive explanation about MDAS, PEMDAS, and order of operations.

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